Caveman already gave the best answer. I'll see if I can add anything to that.
I do get verhy frustrated with my gamemasters from time to time. Ooooh brother, I have some stories I could share. I've shocked a room full of cery experienced gamemasters with the stories, recently. I always had the option of simply walking away. I did once leave a game just last year because it got too stressful for me as a player.
At no point did I ever curse anybody nor tell them to never run a game again. Your gf did the right thing by creating an opportunity for feedback. Whether or not the player's grievance is legitimate is beside the point; it's just jackassery to react that way to a legimate request for feedback.
I don't have a way for you to forget a bad experience from your past. If I did, I would give it to grief counselors around the world. The way you describe your feelings in the matter, it sounds almost like PTSD.
I don't know you, but as a matter of very general advice, I would suggest maaaaybe playing more as a player. Dilute the bad experience with a few new (or at least less bad) experiences, you know? 2020 seems a good time to do that with so much new interest in the hobby and a few semi-professional DMs who have made themselves available over the last three years.