<human>: (I hope this is ok here since I'm am not directly affected by this)
My friend/roommate was dating this girl for part of high school/college. They were dating for about 1.5-2 years before she went to college where she promptly turned to a huge alcoholic/drug addict and cheated on him to obtain drugs. She broke up with him but did not tell him about this. She came back down for break and they hooked up and got back together before she left back for college. Same thing happened but this time she told him what she did and they were done.

6 months later she drops out of college due to failing/drug abuse/depression. Comes back home and they start hooking up again. Around this time she told me everything (she's also a really good friend of mine and this was when I heard about everything that happened as my friend didn't tell me specifics). I tell her about how it's wrong and blah blah blah and she stops. They stop talking too. She gets a boyfriend and he gets a girlfriend, the one he's dating now.

Around 4 months later her and her boyfriend break up. He cheated on her. She and my friend start talking again and eventually start having sex again while he's still dating this girl. This goes on for at least a month before she tells me.

She says he tell her he still loves her and wants to break up with his girlfriend. She says fine but he doesn't and they continue to have sex. I tell her she needs to stop he's being an asshole to both her and the other girl just like she was being an asshole to him when she left for college. She stops it again but now, a few weeks later, I'm in my room and they are on the couch outside having sex. My male friend does not know I know anything about this. She doesn't know I know they're doing it right now.

They're both being assholes and I'm stuck being friends with them and I hate that I'm stuck talking to them when they're being such idiots and especially fucking over his current girlfriend who is absolutely lovely. I do not know what to do. I feel like an asshole for having this knowledge and letting it happen.

Summarize the given text in a few sentences.
<bot>: Guy and girl date. She cheats on him for drugs. They get SOs later. Hers cheats on her. He cheats on his new girlfriend with that ex girlfriend. I feel like an asshole for having this knowledge.