Nikki, who played Rosalie Hale in the vampire franchise, and former American Idol finalist Paul announced their break-up on 29 March.
In a statement, the couple revealed they'd been living separately for the past six months due to work obligations.
A rep added: "They will continue to share their love of music, and are still working on their debut album, I'm Not Falling, releasing in 2014. They remain best friends and look forward to their continued journey together."
Nikki and Paul previously collaborated on a track called 'All I've Ever Needed', which was included in the Twilight Saga: Breaking Dawn – Part 2 soundtrack.
In a statement on her official website, Nikki says that she'd always been too afraid to pursue her love of music until meeting Paul.
"I've always loved music and felt connected to it, but was too afraid to explore that avenue. It was Paul's encouragement and talent that made me feel safe enough to try. We are inspired by the process itself. There is no greater feeling than doing something you love with someone you love."
Nikki and Paul met on the red carpet at the premiere of movie Red Riding Hood in March 2011 – a moment that was captured on camera as Paul was filming American Idol at the time.
They began dating, became engaged three months later, and then married that October in a ceremony held in Malibu
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