My long-distance girlfriend (21F) groped her friend in front of me while she was drunk. (I’m 24M)

Around New Year's, I visited my long-distance girlfriend in the town where she attends university. On New Year's Eve, we had some of her friends from work over, along with a friend of mine from university. We played drinking games before going out. During this time, my girlfriend got excessively drunk and, despite my suggestion to prepare some food together before our guests arrived, she refused. Instead, we ended up having just a piece of toast, planning to grab takeaway in town later. She drank a lot of gin, and although we tried to encourage her to drink water, she declined. When I pulled her aside to say, "Hey, you need to slow down; we still need to get into the bar, and you're starting to drop and break things," she became offended, feeling like I was treating her like a child. I decided to let it go, thinking she was an adult and could handle herself. Once we arrived at the bar, things seemed to be going smoothly, but one of her close friends was working at another bar and suggested we head there for discounted drinks after his shift ended. I declined, explaining that he would be coming to our bar, and I didn't mention that cheap cocktails wouldn't be a good idea at that point. This seemed to frustrate her even more. Much later, we celebrated New Year's, but there was still tension between us, making it hard for me to enjoy the evening. I ended up stepping outside to the smokers' section, where her friend came up, handed me a shot, and asked why we seemed upset with each other. I honestly replied that I didn't even know. At that moment, my girlfriend walked out, approached her friend, grabbed him inappropriately, looked at him, and then walked away. He and I were both taken aback, and I said, "What the hell was that?" He was equally stunned and shrugged in confusion. This incident filled me with anger, prompting me to say, "Forget this, I'm leaving," and I decided to go to another bar with my friend and enjoy some drinks just with him. Now, this situation has shaken my trust in her. I recognize that I have insecurities about her being a young, attractive woman partying at university, and while we've discussed these concerns in the past and had built trust, this incident has me questioning everything. If she could act like that in front of me, I can't help but wonder what she might be doing when I'm not around. In my frustration, I suggested we take a break. She cried and pleaded with me to reconsider, and eventually, I caved. Now that I'm back home, I'm left trying to sort through my feelings. Additionally, she has exams coming up, and I had planned a trip to my parents' apartment in the Alps for skiing afterward. But now, I'm uncertain if I want to do that, especially if she doesn't seem to realize the gravity of her actions. It feels unfair to reward that behavior with a lavish trip. I think I might be overreacting, but I can't shake the feeling that if the roles were reversed, there would be serious repercussions for me simply for approaching a woman that way. It's all very confusing and frustrating, and I would appreciate any thoughts on this situation.