Christina Milian's recipe for mending a broken heart? Put in countless miles on the treadmill, spend some QT with her mom and girlfriends, take on a movie role—oh, and vent about the breakup in a song. "I was in a three-year relationship, and unfortunately he was unfaithful," says Milian of her split last summer from actor and MTV host Nick Cannon. "I found out through e-mail. It wasn't even just one occasion. It was finding out about a bunch of stuff. It was tremendously heartbreaking. I used writing as therapy."

The result is an album, So Amazin' (due May 16), full of songs about love, heartache and bitterness, including the track "Who's Gonna Ride." Is it a shot at Cannon? "I'm not trying to put Nick in a bad light, but I mean, that's what happened," says Milian, 24. "I'm expressing my true, real life. But some of it is based on my other ex-boyfriends." (For his part, Cannon, 25, seems unfazed: "Sometimes you gotta get your aggression out," he told the Chicago Tribune. "I lift weights, she makes dis records. I was the bad guy, so it was coming to me.")

Those days of staying in bed all day crying seem long gone. Between singing and acting—she's costarring with Veronica Mars star Kristen Bell in the summer thriller Pulse—Milian fills her days with boxing ("it keeps away those love handles") and hikes with girlfriends behind her San Fernando Valley home. As for getting back into the singles scene? "I'm definitely dating," she says, "but I'm careful." Yet optimistic too: "I feel like I've moved on, and when you have good energy, good people come into your life."