she cheated on her ex. this is bothering me. confused

It probably shouldn't bother me, but it does.

So today I was with her and she was telling me a story of something that happened a while ago (with her friend. completely unrelated) and in the story she mentioned she just got dumped to give some context, so in a joking way I said "oh shit, you got dumped? what? is there something I should know?" and she said "no" and tried to go along with her story.

So I was acting childish/stupid in a joking manner, which isn't entirely new, and said "he dumped you cause you're too nice, right?" she said "no" so I said, "because he was secretly gay and decided to come out?" she laughed and said "no", then I said "well i'm running out of possible things, it's not like you cheated on him?" in a joking way because I never would have expected it.

Anyway, she just kept quiet. At first I thought she was joking, so I was like "yea, sure, you cheated on him, uh huh" and she looked at me and I went with "no really, did he break up with you because he cheated and he felt bad or something?" I didn't believe her at this point.

And she said she was young and made a mistake, slept with a guy when she went on vacation with her cousins and she wasn't even drunk. She went on with she felt like scum, told her boyfriend weeks after she returned because she felt bad. they tried to work it out but he dumped her because he couldn't accept it.

All this time I was told they mutually broke up. Never asked why because that sort of thing happens all the time.

I was shocked, and kinda hurt by her words. They went out for a little over a year. She cheated on him about 8 months ago. I've been with her about 2 months. She's 21. Was 20 at the time. I'm not really buying the "I was young" part because it's not like it happened years ago, it was months ago.

I'm her first boyfriend since it happened. And I'm a bit worried. Things have been kinda different between us lately, and I was expecting her to dump me about a week ago, but things have picked up and now this comes out.

I don't know if this should be bothering me as much as it is.

She was with him for over a year and cheated on him and this just planted a seed of doubt in my head especially since I haven't been with her that long. I'm not sure if I can fully trust her anymore, even though I want to. I think I'm always gonna have this on the back of my mind. I really don't want this to bother me but it is.

It's a shock. Even now, I can't fully put my thoughts into what I want to type.

Ahhhhhh ****.

"Once a cheater, always a cheater", is bullsh*t. Just because she did it in the past, doesn't mean she will do it in the future. For one thing, she is too young to have formed a permanent pattern of behavior. What it DOES mean is that she is maybe more capable of cheating than somebody , who has never done it at all. A point in her favor is that she told you, and didn't try to lie about it. My opinion is that you need to have a talk with her, and set your boundaries. ANY suspicious activity, at all , is grounds for immediate dumping. Then go ahead and trust her, and hopefully, as your relationship progresses, she will prove herself. Just keep your eyes and ears open. Good Luck!

Well, look at it this way: She now knows that if you cheat, you get dumped. I'd say that's a pretty clear lesson. Aren't you glad she's not learning this at your expense?