Advice on dating

So I (23m)was dating this girl (22f)who’s a mutual friend of my friends. We work pretty good together I like her and she likes me we got some good chemistry and we like each other but she’s told
me once a few months ago after I came back from a trip that she wasn’t ready for a full commitment i wasn’t either and so we go on kinda doing the same thing just hanging out a lot and always being together but never calling it exclusive. It’s been a few months since then and we kept going at it but she came to me a few days ago and told me she’s slept with 3 people and confessing that she felt terrible about it and that she understands if I stop wanting to see her but if that I stayed we’d go exclusive and tried to work things out.

I’m in my head about it all, personally I think since we were not official and I had not asked her to officially be my gf that I can not totally be mad about this since we were not exclusive but I do feel like some trust was broken for how much she was just coming around. I like her and she’s got her wits about her in some ways but she ain’t perfect that’s for sure but I know that the same situation also applies to me. I tried to look at it as karma for being a dick to a last situation ship but I’m not sure really what to do. I’m trying to be mature about this I think I want to make it work but is it easy to forgive and forget just like that.

My question is simply, is it understandable in a young dating society like ours today for a situation like this to occur, like I don’t know if o should be mad or to move on or just forgive and try to start over.