Katherine Heigl would forgive her husband if he had an affair.

The 'New Year's Eve' star has been married to musician Josh Kelley - with who she raises 23-month-old daughter Naleigh - since 2007 and although the actress once believed she would walk away from a relationship if her partner cheated, she believes marriage is always worth working on, especially as they have a child together.

She said: "I've been debating this lately. 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. And 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. Because look at the life we've built together. We have history, we have a child...But at the same time, it would be really hard to ever fully trust that person again."

Katherine loves being married and revealed she doesn't miss dating or the single scene at all.

She told the new issue of Britain's Cosmopolitan magazine: "I don't like one night stands. 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!'"

The couple adopted Naleigh from South Korea and Katherine admitted she was terrified when they first brought the baby home.

She said "The first few days we were shell-shocked and terrified of messing up. I felt a need to protect her - that's just a mothers instinct - but I was also intimidated by her, and nervous that she wouldn't love me. She'd just flown across the world and we were speaking a different language, we were in a different time zone, we looked different...plus she'd been in a really loving, wonderful foster home. For the first three weeks, we couldn't get her to giggle. I was like, 'Oh no, she hates us'."

The new issue of Cosmopolitan magazine is on sale now.