What does it mean?

I think it's her way of saying that she's secure with herself and the relationship. It doesn't necessarily mean that it wouldn't bother her if it did happen.

Maybe she's wondering if you are cheating because of the lack of sex and intimacy and by telling herself that she wouldn't be too upset it's her way of preparing herself to not hurt as bad if it is the case. I suggest that you two go some place nice and embrace each other to regain intimacy. That's more important than sex, I'm sure you already know.

Reassure her that you're an honest and faithful husband that is still hot for his wife and nobody else. Sorry I'm thinking way outside of the box with this because it can mean many things. I feel that it's most likely one of the things I've mentioned. Good luck to you and I hope this helps!

Good advice: do not cheat on her if you don't want to end your relationship with her.

First of all, I would want to be damn sure that is what she actually said. If you can't bring hearing the conversation up to her, then try to breach the subject of the conversation in other ways, possibly by speaking with the friend that she had the conversation with. Maybe even at a time when all of you are together, like when you're out or something. But, do not be direct about it, you'll have to be creative-do it in a joking or comical manner. If you can verify what you think you heard, then it would be time to breach the subject with her. However you may feel about it, do not be angry with her or read too much into something that she said to a friend. It all could just be her trying to impress the friend with a nonchalant attitude.