Katherine Heigl and Josh Kelley
12/08/2011 AT 06:00 PM EST
says she and husband Josh Kelley have always had a zero-tolerance policy when it comes to cheating. But now, she admits, she's not so sure.
"I've been debating this lately," the actress, 33, tells the January issue of British Cosmopolitan
. "Josh and I always said that cheating would be a deal breaker; there is no second chance. But I've seen friends and acquaintances go through it and they've found a way back to the relationship, and a way to forgive each other."
Not that she's giving her husband of four years,
and the father of her 3-year-old daughter Naleigh,
a hall pass or anything. But perhaps a fling wouldn't automatically mean an end to their marriage.
"As much as I would kill him if he cheated because it would destroy me, I have started to question whether, if a mistake were to be made and it was a one-time thing, I would forgive him," Heigl says. "Because look at the life we've built together. We have history, we have a child."
Yet she adds: "At the same time, it would be really hard to ever fully trust that person again."
It's a good thing Heigl, who stars in the upcoming New Year's Eve
, is married – as certain aspects of the single life do not appeal to her, like one-night stands, for instance.
"I don't like them," she says. "I've never met a single woman who has ever walked away from a one-night stand and been like, 'That was awesome! Oh, my god! Best ever!' "