<human>: To begin, I've been in a relationship with her for near 3 years now, and it's had many it's ups and downs. She's a year ahead of me and goes to a different college, and I recently began my college career this month.

I'm no longer sure if I want to continue dating this girl, and I've been feeling this way for the better part of a year now. Last year she cheated on me by making out with other guys on two separate occasions and she chalked it up to 'drunken mistakes.' Naturally, I was enraged upon finding out and she was distraught, but we eventually made-up (somewhat) and began to try and move on. Problem is, I don't think I've ever really been able to do that. I can't ever seem to drive it from my mind--I'll think I've forgotten it, and then I'll remember it at a random time and the feelings of anger and betrayal will just come rushing back. She's since cut off her drinking (from what she's told me) and hasn't been partying as much, but I still have a lot of trouble trusting her.
I've tried breaking up with her once before earlier in the year, but I just couldn't go through with it because she was bawling and seemed really distraught and I'm the type of person that cannot stand to cause people to be upset. So, I didn't go through with it, and we've continued dating up until now.

Well, I guess what I'm asking is this: should I continue to date this girl, or should I just go ahead and break it off? And if I do that, how should I go about doing so in the least-painful way possible for her?
Throwaway for obvious reasons, and she browses Reddit (maybe even r/relationships, I don't really know).

Can you condense the text into three sentences or less?
<bot>: Girlfriend of nearly three years is LD at another school, has cheated on me in the past, and I'm unsure of how to proceed. Help?