Amanda Seyfried Unsure If Her Boyfriend Is 'The One'

Dominic Cooper might want to start penciling in his dates with Amanda Seyfried.

"A lot of people ask me, 'Is Dominic the one?' I don't know, and I'm fine with that," the Letters to Juliet star tells Teen Vogue in its June issue about her British beau – and former Mamma Mia! costar.

Instead, the actress, 24, thinks it's best not to get too far ahead of herself.

"Too much planning can lead to heartbreak," she says. "Love is great and possible always, but it's very rare to have the feeling that 'I want to be with this person forever.' "

Still, that doesn't stop Seyfried from taking roles in romantic comedies. In the last year, she's starred in two – Dear John and, now, Letters to Juliet.

"It's fun to play characters who have these ideals you don't have," she says. "Like, in Dear John, Channing [Tatum] and I had such a good time because we were pretending to be in love."