No need for you to feel humiliated for her broken behavior -- none of that reflects on who you are.
If only that came easier to me. I've always defined myself in large part as "us", we were together from such a young age it's a huge part of my identity, so it's hard/impossible for me to see her behavior as not reflecting on me in some way. Part of the issue is that I used her to pacify my own insecurities in a very superficial way - "I have a hot/cool/fun girlfriend, therefor I have value". Her behavior then makes me think the opposite, and confirms my insecurities - "You had a girlfriend that was too hot/cool/fun for you, you are not cool/hot/fun, so of course she did those things".
And for me, the determining factor is -- was that behavior truly out of character or a greater reveal about who you're with?
In that sense, if you're not sure, I can see why the anger is hanging on, because you don't feel 'good' about the future. But if she really is changing, really a better person now, then you do have a chance to build something better. Of course, you're under no obligation to offer this final chance.
It will come to whether or not you can see who she is now versus being haunted by who she was.
I struggle with this because on one hand I know she is not that person anymore and is genuinely disgusted by a lot of the ways she acted. On the other hand, as I have documented elsewhere, she continues to act in impulsive/reckless ways, just in a much more subdued way, but it still makes me nervous and mistrusting. I.e., sending a flirty text to our babysitter, going for a walk with her COW, etc. She now has the peace of mind to disclose these things and want to change them rather than hide them, but it scares me that she still does things like that. It makes me think it's a built-in feature of "who she is" that isn't going away, that it can only be managed, and often managed poorly.
@BFTG
In hindsight, had we stayed together, I'm certain her infidelity at that stage would have been just the tip of the iceberg in terms of the crap she would throw my way through the years. So, I have learned to be grateful for what she did, because I'm pretty sure my present-day reality would really suck had we stayed together.
If I had known what my WW did back then and left her, I would surely, 100%, without a doubt harbor the same thoughts about her as you do about your XWGF. If I had shown up here at 21 years old and my story was "my girlfriend had an affair," or even at 26 and the story was "my fiancee spent a day drinking and smoking with a random guy overseas", the advice would be unanimous - get out, leave, you're lucky she showed you who she is before you married her, etc.
It's a big part of the mindfuck for me - everything about her behavior back then screams "run, don't walk, away" and I feel certain that if I knew the whole truth, I would have. And if I did, then in the present I could make up whatever story about who she is that I want, and I could feel satisfied that no matter how my life turned it, it must have turned out better for her not being in it.
But that didn't happen, she hid it away and pretended to be someone she wasn't, faked it till she made it, and now I'm stuck reviewing my history and trying to make sense of it and trying to figure out what pieces of her I can trust, which parts of her are real, and who she is deep down and who I am to her deep down.