<human>: So I (24F) live with 3 people, including my ex (23M) of one year and my best friend (23F) that I've known for about 9. Just for context, I dumped my ex after a 2 year relationship. We have all known each other since high school or so. 

It came to my attention this weekend that there's some mutual attraction between them. She got super drunk at a party and he was shut in her room with her for a few hours, presumably just taking care of her and making sure she was okay. Tbh I've also noticed other small things over the last few months since she moved in, like him sitting with his arm around her when he's showing her how to play a video game. 

It's really not that I have feelings for the ex (like I said I dumped him) or even any sort of weird possessiveness over him, it's just that

A. I feel like it'd be super weird for them to date, especially while I'm still living here (arrangements will likely change by next fall). Not sure how else to describe that feeling besides uncomfortable.

B. They're my absolute best friends and I've known folks I the past who started dating and never spent any time with anyone outside of the relationship. So I guess I'm scared of losing them as well. 

I talked to her about it earlier today and expressed my fears and feelings about it, and she said she was fine with not doing anything. But she's also the type that would literally do whatever a friend might say just to make sure they were comfortable.

Could you distill the essence of the text into 1-3 sentences?
<bot>: Roommates best friend and ex have mutual attraction. I feel super uncomfortable about the whole thing and I have no idea if that's reasonable or not. Halp.