The short version is, she realised that she liked someone she worked with, and decided then and there to break up with me.
The long version:
I'd been with her for 6 years, give or take. I'd spent the past year or so saving up for a big surprise that I was going to tell her about on Valentines day this year. (She'd always wanted to go to Japan- I'd just about saved up enough to take her there during hanami in 2019. I'd planned to propose to her while we were there.) Things felt a little rocky, mainly due to the both of us being down thanks to our living situations at the time- mostly frustration stuck living with our respective parents, unable to afford to live with one another etc. but we spent a week away with my parents a few months before and everything was great, so I thought we were okay.
December 10th, we met up and went for a coffee and lunch at a local cafe, and everything seemed great. She then brought up moving in together, and suggested that perhaps we should rent somewhere so we can do it NOW rather than having to spend years saving for a house or apartment. I go home genuinely excited and hopeful for the first time in months.
On the 12th, TWO DAYS LATER, she messaged me after she got back from work asking if I was free the following Friday, but wouldn't tell me what it was about. (Expecting me to go through the whole week worrying about what she wanted to say) Finally managed to get it out of her that she wanted to break up.
We met up the following morning and.. that was that. She made sure that we'd meet before Christmas so she could still get her presents, and insisted that we should still remain friends. After that point, she proceeded to become more and more off with me and verbally abusive. After I wouldn't stop "guilt tripping her" (by having feelings and being upset, and not understanding what had happened), she ghosted me. Blocked me on everything, entirely cut me off. When she unblocked me some time in March, she was acting incredibly secretive. I asked if she liked anyone else, and she said yes. I guessed that it was the guy she works with, which she then confirmed. Her whole story seemed off somehow, and she was really dodging any questions I asked.
I finally got her to admit that she'd got his number and they'd been "hanging out pretty much all the time". Going by her version of events, she got his number about a week after we broke up. However I'm not entirely convinced that it wasn't the same night that she broke up with me, given how evasive she's been about the entire thing. I asked if they were officially "girlfriend and boyfriend" and she wouldn't answer, saying that they "hadn't had that discussion yet"- a response that she clearly hadn't thought, given that her new boyfriends facebook profile reads "In a relationship since 22nd of January".
This whole time, she insisted that she wanted to be friends still, yet remained verbally abusive (last thing she said to me was "just fuck off" before blocking me again). This was in response to me asking to see her or even just speak to her on the phone or... anything really, just to allow me to get some kind of closure, and say bye to her properly. She has since told me that she doesn't care about me, my well being or what's going on in my life, and has generally made me feel like absolute shit, and blame myself for everything. She slowly ground me down to the lowest point I've ever been at in my life. It's taken me almost 11 months to get to this stage where I can look back and not blame myself.
She crushed me in the most spiteful way that she possibly could, and then blamed me as if I were being unreasonable by being upset by her behavior, after having poured every ounce of my heart and soul into a relationship for 6 years, only to get fucked over by her at the end of it.
It's taken me 10 months to get to the stage where I can look back now and see that I probably dodged a bullet in the long run, and say "fuck her". Funnily enough, in retrospect, I can see a lot of narcissistic tendencies in her behaviour. Reading a paper on narcissistic personality disorder feels like reading a paper on her. However a year ago I'd never have been able to see it.
In closing, I just wanted to say "If you ever read this: Fuck you R, I hope he makes you as miserable as you made me- perhaps it'll give you some perspective on your on actions. You're a childish, self centred coward and a narcissist, with all the emotional range and maturity of an 8yo. I retract any apology that I have offered you- you deserve to feel guilty."