My ex girlfriend slept with my best friend because she thought I was too "emotionally unavailable"

So I'm 17 I'm a senior and I've been dating this girl for 8 months so we're having sex and one day she dumped me for my best friend who i know since childhood. I was shook! She told me it wasn't personal it was because I wasn't "emotionally available" and I was a "loner" who didn't care about others and didn't like to go out. So she ended our relationship and started dating my supposed best friend and i found out so I asked her if the whole time we were together was she just a fucking user then she said " yeah I'm sorry if I hurt you but it was worth it because I had hot sex with your best friend" so I've been sad for a few weeks and I had to start therapy too because she really messed with my head. Also, to make this whole thing worse she told me she didn't tell my friend about any of this and she told me she did it because she didn't want to ruin whatever he had going. So she just used me? Like I thought this girl cared about me but it turns out she was really just using me. It's hard to believe. I asked her if she ever loved me then she said she was "Fake dating" me. Note: I'm a loner because I had a lot of fights in my school due to being bullied. So it was better for me to be alone. However, i did have a few friends and i also told her i would share her photos with all my buddies in school if she broke up with me. So whatever I had going it was just a waste of time. I'm about to graduate in a few months so I'm going to do whatever it takes to become better, do therapy, work on myself, etc. she really messed with me. I asked her if she could do anything she'd like what would she say then she said " yeah I would be a porn actress" so I'm like okay cool. This whole story just shows that women are evil and manipulative.