Amanda Seyfried's career is hotter than ever -- and so is her love life!

In the April issue of ELLE, the 25-year-old Red Riding Hood actress finally confirms that she's been dating actor Ryan Phillippe, 36, since they met at Kate Hudson's Halloween party last October.

"I've been 'seen' with him," she says coyly.

It shouldn't be surprising that Seyfried is reluctant to talk about her casual romance with the Lincoln Lawyer star; her previous relationship with actor Dominic Cooper ended abruptly after she discovered he was still seeing his longtime girlfriend.

PHOTOS: Stars caught cheating

"I was just kind of foolishly thinking that the two of them were done and Dom and I were involved. But we weren't really as involved as I thought. So I got my heart broken pretty hard," Seyfried says of Cooper, her Mamma Mia! costar. "And then it took a long time for us to break up again. After that, it's really hard to open myself up to a new person. Really hard."

In fact, she admits that the split ruined her chance at a relationship with True Blood's Alexander Skarsgard, 34.

"We dated. He's super funny, but I was too involved with Dom," Seyfried admits.

According to the actress, it wasn't hard to fall for her Mamma Mia! costar on the set. "It's one of the easiest things in the world. You're both open. You're put in a situation where you have to make out with each other," she tells the fashion mag of Cooper, 32. "It's easy for things to get carried away."

As for her best on-screen kisses? "I can't lie. It didn't suck making out with Channing Tatum and Justin Timberlake."