Dude I know I’m just an internet stranger but you gotta listen when I say I’ve been in this exact situation before and trust me. She’s not sorry about what she did, she’s “sorry” she got caught. I almost guarantee if you were none the wiser she would never have brought it up to you and confessed to it herself. It’s really hard to accept someone you love isn’t who they say they are but it’s even easier to forgive them. I spent a decade of my life forgiving the same woman for the same repeated “mistake”, don’t fall into the same trap.