GF kissed another guy (long)

I 24M started dating a girl I'll call X 23F. Both of us are in law school — I'm am 2L she was a 1L at the time.

The start of this relationship was honestly the best I'd ever experienced. She was affectionate, funny, smart, beautiful — an instant connection I hadn't had with anyone before. She'd tell me all the time how lucky she felt to be with me, how happy she was.

For context, she was upfront early on about having OCD, including a specific subtype (ROCD) that affects relationships — comparing partners, comparing the relationship to others, that kind of thing. She'd been in ERP therapy for about a year before we met, and I respected that a lot.

About a month before finals of my 2L year (we'd been together roughly 4 months at this point), things started to shift a little. She got more distant, we were both obviously stressed, and I chalked most of it up to finals looming.

Around two weeks before my first final, she went out to the bars with people from her org unexpectedly — didn't tell me beforehand, even though we'd specifically agreed to keep each other posted when going out. Not a huge deal on its own (I'd done the same to her once before and she was understanding), but it stood out because of that agreement.

A few days later I found out she'd cried to a guy friend of hers that night — a fellow law student, not someone in my circle — about "cognitive dissonance" over the type of legal work she'd be doing that summer. When I asked why she hadn't come to me with that instead, she said, "because you wouldn't understand" — which stung, given I was in the same field. This same guy ends up being important later.

That same week, she invited me to a law school org's end-of-year social at a professor's house. I was genuinely looking forward to it — one last night to relax with friends before finals buried us.

The week got worse before it got better, then a lot worse. The day before the event, I was in class and got a text from her saying she'd been picking at her face all day, crying, overwhelmed — she asked if we could cancel a dinner I had planned with my parents. Of course I said yes, canceled, went straight to her afterward, and spent hours consoling her.

The next day was the event. I ended up asking to leave class early so I could catch the bus down with her and our friends instead of getting a ride separately — she'd been newly elected to the org's board, so she was already taking the bus. When I told her I'd made it work, her response was basically "why, you don't have to, it's kind of a board bonding thing." Deflated, I rode down separately with a friend instead.

At the event, about an hour in, she leaned over and told me — while I was sitting right next to her — that this was basically "a (her name) only event" basically telling me she didn't want me. So I was stuck at a house 45 minutes from campus, a week before finals, effectively told to get lost.

For the rest of the night, she spent her time talking to that same guy from the bar a week earlier — flirting, in front of me, my friends, and future colleagues. It was apparently obvious enough that the attorney hosting the event at his own house actually thought the two of them were a couple. A friend later told me they'd sat together the whole bus ride down too and talked (so much for board bonding). When we got back to campus that night, I saw her walking off with him, alone, toward the neighborhood above school. She didn't respond to any of my calls until the next day.

Genuinely one of the worst nights of my life. Embarrassing, humiliating — in front of my friends, her friends, and people I'll be working alongside for years.

When we finally talked, she apologized and said her OCD had flared badly that week and she "didn't really realize" how she was acting. She also told me she couldn't fully promise she'd never cheat on me — something about her OCD making it hard to promise anything with total certainty.

I asked directly the day after the event if anything happened with the guy that night. She said no.

Turns out she found out they'd kissed just 3 days after the event — he'd apparently told her. She sat on that for three full weeks and didn't tell me until the day before I was supposed to move for my summer associate job. When she finally told me, crying on the phone, she said she didn't remember the kiss itself because she was blackout drunk that night. She cut off communication with the guy but this feels really wrong and I'm hurt.

What are your thoughts?