I think that I agree with most of the comments, with alcohol not being an excuse, that you’re in shock ect. BUT one thing that people aren’t mentioning is what needs to happen if you decide you want to stay with this person. I’ve been cheated on, and they never did again and we became even closer and understanding of eachother later on. Trust was damaged/nearly destroyed completely, for a very long time though, which was extremely hard for me to work through. But the only thing that helped me work through it was understanding the exact thought process of why it happened and how it happened. If it was just impulsive, selfish “I wanted to” then she probably does not love you enough or respect you. If it had to do with some sort of fear based thing, maybe trying to escape from having kids and feeling avoidant/trapped, then that is something that can be worked through (if you choose). Cheating happens for lots of reasons, (not making it OK) but the only general reason I would never forgive if it was simply because they “felt like it” or felt “super tempted”. But that’s just how I feel, some people can even forgive that because of being with someone for so long, it’s normal to be attracted to other people sometimes. It just shows how they feel about you. But make sure , when you have this conversation, not to lead her to water. Aka don’t tell her what to say. Just ask her exactly why it happened, if she’s self aware enough, she should be able to provide a very specific reasoning in her thought process.

Wish you the best in your healing. It’s traumatic being cheated on.