This is very similar to my situation though mines alot more longer and complicated.
Here begins, I liked a girl and she liked me, my friend who I used to talk to about my feelings about her decided to go out with her. I forgave him when he told me as I always value friends > relationships.
Later on in the year she comes to me crying and telling me about how he is abusive towards her (I wont go into specific detail as it will take too long).
I comfort her and tell her that his probably just stressed out as he doesnt act like that normally.
Few months pass and I find that we pretty much stop communication (me and her) for a period over the months, then One day same thing happens she comes to me crying about how he is abusive (at that point I didnt believe her until I saw it myself).
And then few weeks later it continues and she falls into a depression until finally they break up for the first time, at which I took her out to try to cheer her up (which successfully did).
Then later on during that day he finds out that I went out with her that day and my friend wants to get backtogeather again with her promising her it wont happen *Again*.
We (not only me helping her from here on) tell her its best that they stay apart, however they get backtogeather again, what I didnt know at that point was that she liked me and always had. (She had talked about her feelings to my friends and they tried to help her about it)
After they get backtogeather again for the first time i confront my friend about it and he makes me apologise for helping her.
Few weeks after that she has been pretty much given strict rules to live by (for some reason she was scared he would break up with her, and she wasnt allowed to communicate/go out with friends, stay up past 11 etc... by her bf (my friend) We suspect this was so he would try to eliminate any possible way of us helping her.
After a while well the abuse happens and the same breaking up/getting back togeather process goes on for about 4 months, eventually she confesses to me that she had and always liked me and then from there on it gets even more complicated.
She is forced to choose between the both of us, I tell her that whatever her decision is is her decision and I shouldn't have any influence on it, while my friend uses lies to win her over.
We talk and somehow he gets me to apologise for having feelings for her.
And now their still going out and I have nfi or even care anymore with my other friends who were also slightly involved and helped counsel all parties involved not careing at all anymore hopeing that she will eventually realise the truth even after many people have told her what kind of person he is.
edit : also forgot to add we were gona go to formal togeather but she went with him instead and he made me pay for her ticket to go with him.
But even then I forgive him as his only human and we still remain as friends.