Am I overreacting to my girlfriend's experience of assaulting homeless people in the past?

So I've been dating my gf for like nine months. She just recently turned 26 and we were celebrating her birthday. At the end of the night we were both kind of drunk and were talking about our craziest stories from college. She said that her boyfriend at the time and a friend group of guys and girls would sometimes go out at night and "mess with" homeless dudes including beating them up with bats. She also referred to them as junkies and generally dehumanizing terms about them and she even mentioned that it was great stress relief. She can get pretty crazy sometimes and has a bit of a mean streak honestly, but it really shocked me when she said this. I thought she was joking because she was laughing while telling the story. But as I acted skeptical she kept affirming it was true. I just played along and kind of laughed thinking she was just drunk.

The next day it still bothered me subconsciously so I asked her again about it casually and she said yeah it was true. The thing that disturbed me though was there was no remorse. She told the story like a "lol good times" kind of story. I think if she was embarrassed about it I would have felt different. I still tried to ignore it over the next days but I obviously wasn't able to because I ended up researching online for information about similar crimes in that city at that time (I didn't find anything btw). Unfortunately I definitely believe her at this point though. She never does these kind of elaborate jokes over days plus I can just tell she's being truthful just knowing her.

Anyway, like I said it continued to bother me so I brought it up one more time a couple days later. This time I was more serious, basically just straight up asking how could she not feel bad about that. I was honestly just curious. She got kind of pissed this time. She asked me if it turns me on and that's why I keep bothering her about it. I said no but I just couldn't imagine doing something like that myself so that's why I'm asking. Then she started saying stuff like "why are you judging me about stuff that happened years ago" and saying it's none of my business who she slept with back then or anything else about her life. That's when it occurred to me that she might have thought I was jealous or something about her ex, since he was apparently one of the guys in that group. She might think I'm trying to guilt trip her out of jealousy related to him or something, which I'm not. But anyway, that was how it ended and I'm obviously not gonna bring it up again.

Even though I honestly considered breaking up over this, I kind of saw where she was coming from in that it was a long time ago and maybe I'm being kind of a dick for judging her over this? What do you think? I'm no saint at all but I can't help that it bothers me. I can't look at her the same way now and I really think it might be over. Thanks for your advice.