[Serious] Friends of people in relationships you don't approve of, why don't you approve and what was the last straw?

a former best friend of mine was obsessed with a guy, she met at college, we'll call him B. i went to visit her right before junior year started, and of course, we had to see if B was home. turns out he was. I hit it off with B's roommate, who is still my boyfriend, after 7 years. I guess she didn't like that I began dating B's roommate, so she made it her mission to make B hers. she was turning into quite the alcoholic and would do whatever B wanted. fast forward the night of my boyfriends 21st birthday. I had planned a surprise party for him, at her house. she is no where to be found, either is B. this aggravated me. I realized I forgot something in my boyfriends room, so we drive back to his apartment, and as we open there door, there she is straddling B on my boyfriends futon. needless to say, I was done with her. long story short, she turned into a borderline alcoholic, dated B for two years, after they broke up she followed him up north, and then ultimately moved home once she saw he had a new girl. congrats bitch. way to ruin a pretty good friendship.

/r/AskReddit Thread