Don't Know How to React

I have a very close friend, let's call her Ava. Ava is very kind and humble, and she always listens to me and helps me. She is genuinely happy for me when I do well. I am EXTREMELY concerned about her marriage. Every time I talk to Ava she complains about her husband and tells me how awful he is acting or how they aren't getting along. Ava has a history of being the victim in abusive relationships and abusive family dynamics. Her husband isn't physically abusive but he's mean and controlling and toxic. I loathe him. She also suspects he hasn't been faithful to her. With this context in mind, Ava told me today that she cheated on him. I don't want to be judgmental but it does bother me that she would cheat, even though her husband is terrible and I deeply hate that he probably is cheating on her. I feel like it is hypocritical of her to cheat on him when she was so concerned about him cheating on her. She already feels incredibly guilty about it so I felt like I couldn't show that I was bothered by it. I didn't want to hurt her because I genuinely care about her. It's a triggering subject for me because my dad cheated on my mom. I really despise cheating. I think it would be better for her to leave him than stay overwhelmed in this dramatic mess, and I worry worse things will happen if they stay together. I want to keep being her friend but I feel like I see her differently now. Can someone explain why this happened? What do I do with these feelings?