What's up guys- first post here, wanted some feedback

Began dating my ex girlfriend back in 2018. About 6 months in I began to realize the girl was different, not in a good way, but in a pathological lying, constant need for validation, cheating kind of way.

Began researching and discovered she was borderline (BPD). I was emotionally invested in the relationship at that point and thought I could white knight her out of the illness.

Realized that was futile undertaking and became more and more fed up and red pill with her until I dumped her and went no contact

Felt great, I am a good looking dude and always been good with women so I was out hooking up and picking up old hobbies. Felt like I got my life back and had little to no thoughts about ex bpd

About 4 months go of no contact and I got a call from I number I didn't recognize, ended up being her and we started hanging out over the course of a week. Realized that was a mistake and ended it again, and went no contact July 5th of this year

A few months prior to us hanging out again I began renting out a room in my condo to a guy from Craigslist. Seemed nice enough when I interviewed him but quickly realized this guy was narcissistic and grandiose. He's not a particularly good looking guy and seemed to tell a lot of white lies to bolster his shaky self esteem. I realized this and never hung out with him or interacted at all- as long as he paid me rent I can look past his personality, we don't need to be friends to be roommates

Anyways.. one of the last times I hung out with my ex we went out drinking with a couple of her girlfriends. One of her gfs was asking if I had anyone I could hook her up with and I decided to invite my roommate along. Roommate and her gf hook up and I thought that was that

Roommate seemed very interested in my ex as she is an extremely attractive girl. I noticed it and took it more as a compliment than anything

I end it with ex shortly after and go no contact again. She is extremely hurt leaving vms from blocked #s and posting subliminals about me online. It's been 6 months since we last spoke and I have NO intention talking to her again

Come to find out she starts seeing my roommate (not my friend, I don't like the guy or speak to him) a couple months ago. He hasn't said a word about it and I haven't told him know

I decided to give him 30 day notice around the time I found out under the guise that I am purchasing a multi unit property (which I am, but not this soon).

I guess my question is- is she doing this out of spite? She has always been an overly emotional (bpd) and spiteful person. I kept frame and haven't brought it up to him or her, what's the best way to go about this?

Just looking for some support, I want to beat his ass but know doing so she would win and get pleasure from it. Feels like a lonely place

Thanks guys

-D