Simon Wilcox has co-written hit singles before, but last year one of her collaborations became a bona fide smash.

“Jealous,” recorded by Nick Jonas, sold more than two million copies, and reached No. 1 on the Billboard Dance Chart, No. 2 on the Billboard Pop Chart, and the Top 10 on the Billboard Hot 100 Chart, as well as both the U.K. and Canadian Top 40.

The song – which Wilcox co-wrote with Jonas and Nolan Lambrozza (both BMI) – also reached No. 1 on the MuchMusic Countdown. Jonas has performed it on Late Night with Seth Meyers, The Today Show, and The Ellen DeGeneres Show, among other high-profile TV appearances. The video has been viewed more than 87 million times on YouTube.

On top of that commercial breakthrough, this year her new publishing company, Dames, Booze and Chains Inc., signed to Stellar Songs (Sam Smith, Charli XCX), via Sony/ATV Music Publishing. Stellar is run by the songwriting/production duo Stargate, who have worked with some of the biggest names in music over the past decade, including Rihanna, Beyoncé, Katy Perry, Jennifer Hudson and Mariah Carey.

“I’m so lucky,” Wilcox tells Words + Music on the phone from Los Angeles, where she’s lived since 2007. “Because I have the boutique side, which is Stellar, and then I have the major publisher powerhouse, which is Sony ATV. They’re working together, and on top of that the brains behind the whole operation was my manager, Dan Petel. He is the visionary. He set up the Nick Jonas session. He found me through my songs. He started hearing my songs and thought, ‘I like this.’”

Petel came on-board after Wilcox’s seven-year relationship with EMI Music Publishing Canada ended in 2011. Wilcox wasn’t ready for another publishing deal at the time, but her longtime friend Cheryl Link from Peermusic convinced her to sign what became a three-year administration contract with Wilcox’s own publishing company at the time, Fun Cooker.

Although Wilcox is more than a decade into her fruitful career as a professional songwriter, you can still hear the wonderment in her voice when she talks about the great unknown – her fellow co-writer or writers. It takes a certain kind of person to be able to collaborate with just about anyone — the shy, the moody, the know-it-all, the deep, the joker, and so on. It’s not for everyone.

Wilcox got her first opportunity after self-releasing her debut EP, Mongrel of Love, in 1999. Quebec singer-songwriter and cellist Jorane heard it and asked Wilcox if she wanted to write with her. Their song “Stay,” released in 2004, reached the top of the Bravo chart, earning a SOCAN No. 1 Song Award. Within a year, Wilcox had two more No. 1 songs, “Tell All Your Friends” for Francophone Brit-pop style act Projet Orange, which topped the MuchMusic Countdown, and “Home” for rock band Three Days Grace, a chat-topping hit in Canada and Top 10 in the U.S.

“I’ve been doing this a long time now, and I’ve been lucky in that I’ve had pretty consistent success, but I try not to think about it,” says Wilcox. “I try to focus on the process. Am I doing my best? Do I feel like I’m pushing boundaries? Are these new ideas? Do I love these songs? How can they be better? I just try to think of success and failure as by-product of me doing something I love.”

Today, her published songwriting credits include Walk Off The Earth, Scott Helman, Trevor Guthrie, Petula Clark and Josh Groban.

Wilcox continues to work with Jonas and Helman, and this summer she was in the studio with Britney Spears and songwriters Ian Kirkpatrick and Chantal Kreviazuk. She has two co-writes on 5 Seconds of Summer’s upcoming record. At the globally televised 2015 PanAm Games closing ceremony in Toronto, Serena Ryder performed “Ice Age,” a song she and Wilcox wrote with Sony/ATV songwriter Thomas “Tawgs” Salter for Ryder’s forthcoming album.

“The minute I started collaborating with other people, I realized that I had this closet band fantasy, that I wanted to work with other people,” says Wilcox. “I’m interested in what people have to say. I’m interested in what their ideas are and I think, as artists, when we work alone, we tend to travel the same neural pathways over and over again.”

So what does Wilcox bring to the table? “Fresh blood,” she says. “All of the people I’ve worked with are fully capable of writing massive hit songs on their own. It’s not like they need me. It’s just that maybe I bring some value that’s new, that’s unexpected.”

Wilcox started writing songs in Grade 5. Although her father is noted blues-rock musician David Wilcox and her mother was a record producer at the time, she was raised in Ottawa by a family friend from age three until she was 16 years old. “I just knew that I wanted to write songs,” she says. “It never occurred to me that it was a career that I could have.”

In her late teens, Wilcox moved to Toronto to attend the Ontario College of Art and Design, but kept writing original songs on guitar, or piano. In 2003, she signed with Sony BMG for her album Smart Function; right before it came out, EMI Music Publishing Canada’s Michael McCarty and Barbara Sedun (now both with SOCAN) signed her.

During her time at EMI, Wilcox wrote with fellow EMI signing Gavin Brown, and with (or for) a range of artists, from rock bands like Three Days Grace and The Trews to many of the Canadian Idol winners during writing camps. In 2007, the company helped her relocate to L.A. to further her career.

She’d always shown professionalism. At EMI, McCarty used to tell her, “You’re the first to arrive and the last to leave.” “I feel like there were a lot of people in my world that didn’t believe in me,” says Wilcox. “I was really determined to prove them wrong, that I was worthwhile as a human being and not just as a songwriter. But songwriting was a way for me to show people that I had insight and I had value.”

Wilcox had her own Top 10 hit as an artist in 2004 with “Mommies & Daddies,” something she’s clearly proud of, and she still writes songs to sing for herself. Her last solo album was 2007’s The Charm and the Strange, but a few years ago she started a duo with U.K. artist Shridhar Solanki called Cider Sky. They performed at the 2010 Olympics in London; their song, “Northern Lights,” was on the 2011 Twilight Breaking Dawn – Part 1 soundtrack; and they released an EP called King.

“I had this idea,” says Wilcox. “I spend so much time writing songs about my own pain and suffering that I’m bored with it. I thought maybe everyone in the world was feeling some pain and suffering, and didn’t want to hear about mine,” she laughs. “And I wanted to make music that was pure joy, that’s totally uplifting, without being cheesy or weird about it in any way.”

Still, the main thrust of her career is as a songwriter who most often writes with others, and for others. On this day, she’s up by 8:00 a.m. for our interview, then has a session with Evan Bogart, a.k.a. E. Kidd, who wrote “Halo” with Beyoncé. “It would be a rare day without a writing session,” she says. “I would probably work on songs that are ongoing, stuff that I haven’t finished, or I’d be thinking of song ideas that are original.”

That’s how “Jealous” came about. Wilcox had a studio session booked with Nick Jonas and producer Nolan Lambroza. She was sitting with Jonas in a parking lot trying to figure out a topic. “He was talking about jealousy in his relationship and he said he thought it had its place, and I thought it was so exciting,” she says. “I just said, ‘I want to write about that,’ and we wrote the song very quickly, maybe in an hour.”

Other times Wilcox might not meet the artist at all. Such was the case with Petula Clark and the song “Next To You,” which she wrote 50-50 with producer John Williams. Nor did she meet Josh Groban, where the song was a three-way split that came through Tawgs Salter.

“Tawgs is a longtime collaborator of mine,” Wilcox says. “We worked together on Scott Helman and Walk off the Earth, and he’s worked with Josh Groban a long time. He called me and said, ‘Do you want to work with me on this a little bit?’ and we worked on it together. I’ve never met Josh. I was at my kitchen table.”

When she does write with an artist, Wilcox does her prep work beforehand. It could be as simple as brushing up on the person’s catalogue, or if it’s a new artist, she might be given a private link to their music.

With Helman – the 19-year-old signed to Warner Music Canada – Wilcox started writing with him when he was 15 and didn’t yet have a major label record deal. His debut EP has three songs co-written with her and Salter, “Bungalow,” “Machine” and “That Sweater” – the latter awarded a SOCAN No. 1 Song Award for scaling the peak of the CBC Radio 2 Top 20 Chart. Although she has a lifetime of experience compared to Helman, Wilcox didn’t consider herself a teacher by any means.

“We’re equals and we’re collaborating,” she says. “He’s always been a great writer. I remember hearing Scott’s stuff, recognizing he was a poet and just wanting to be there.” And what of writing in the mind-set of a teenager? “I feel like a perpetual teenager,” she says. “I feel angst-riddled and frustrated and insecure and confused every day of my life, so it’s really not a big jump.”

As the interview wraps up, Wilcox, who often has to get her co-writers to open up to her in order to write genuine lyrics, unexpectedly does the same – and in the process, reveals one of the keys to co-writing songs.

“You asked me what makes a good co-writer?” she says. “I went through five years of super-intense therapy. I went to two sessions a week. I think there’s some element of that [in co-writing] – that kind of listening, and patience, and hearing each other, that happens in the container of a therapist’s office. I don’t know if there’s any way to write about that that doesn’t sound scary or insane, but there’s an element of [co-writing] that’s therapeutic to both people, talking everything out, and being real, and being genuine, and really listening to each other. When songwriting is at its best, there’s a moment of real connection between the people that are writing.

“There’s a profound listening that has to happen between both people, and that listening is something that I learned through therapy. I’m sure most people don’t need to learn it that way, but I learned it that way. It’s a beautiful moment of connection between two, three, or four people.”