I (21M) am upset over recent break with girlfriend(22F)

So me and my girlfriend have been a couple for about 2 years, and we’ve had on and off fights over me not being romantic enough and her being mean and rude in response to that. We’re both seniors in college right now, and I admit I do tend to get lost in my work since I’m not in the best academic position. We went on break a few months ago because she insulted me and I was stressed about finals, during which we would regularly see each other and do relationshippy stuff, just without the titles. I was going to mend things over and be more romantic after finals, but she just so happened to get a paid trip to LA by some NFL player, which she tried to hide from me. She left me with her dog to take care of because she didn’t want to pay someone, and had me drive her around to get her ready for the trip, which again I didn’t know was some fly-out date. It wasn’t until a few days before the trip where I asked what the trip was for when she told me after I did some snooping. I expressed how angry and upset I was, and yet I still tried to mend things over when she got back. A few months later, I find her tweeting jokes about the whole trip and I decide to ask her if she had sex with the guy while she was out. She did. We broke up again and she told me to get over since we were on break, and I decided to try to get over it.

TL;DR:
I’m upset my girlfriend had sex with someone while we were on a break. A break in which we still did everything we used to do.

With all this, it still feels like nothings been fixed between us, other than me being more romantic as I’m no longer struggling with class work and her not being as mean to me. So I ask, should I be angry at the fact that she did all this? Should I just get over it and try to make things work out? Should I leave for good? I’m genuinely at a loss here.