best friend or best guyfriend.. ah, help?

[arr]

okay, so one of my best friends dated this guy for a year. and in the process, i became best friends with him. she treated him like crap, so they eventually broke up. he's bipolar, and i'm the only person who understand him. now he tells me he loves me and stuff, but i saw on twitter that he still wants to get back with her. he says he didn't lie to me by saying the nice things he said to me, but he realizes i'm upset that he still likes her. she never understood him, and she never will. should i let her hurt him again? or should i follow my heart and keep liking him despite her? i don't want to ruin my friendship with either of them, but i've accidentally gotten in the middle of this. i thought they were over. i was wrong..
we're 16-17, by the way.

[lisa]

neither go lesbian. WOOOOOOOOOOOOOOOO

[trh2000_2000]

If your 18, have sex with him. If he still likes her then, have sex with her. If she likes you, then have a threesome with him, and everybody wins.

[Christine...]

I would stand back and let the situation play out. Then decide when they break it off what to do next.