Definition: Given a real-life anecdote of a complex ethical situation, generate a suitable title that describes the main event/root cause of the situation. Imagine that the given text is a social media post, and you have to write the title of the post, so the users can decide to read the main text or not.
Input: My boyfriend "M" has a female friend "P", who he previously had a thing with in October (while we were not together). Once we got back together, he stopped hooking up with P but never told her he was dating me; he would always avoid telling her when he was with me, telling her white lies and withholding the truth. So P had developed feelings for M while they were together, and M knew she still had feelings while he and I were already together. She told him she needed to confess something, and M has been putting it off for weeks. Basically, he's ignoring the whole situation (that she's in love with him) while still being friendly with her. 

I've told him this situation bothers me and to fix it, which he always agreed to but never followed through. To me it seems like he's leading her on, plus I don't particularly enjoy being kept a secret. His reasoning for not telling her is that he didn't want to make big drama when it wasn't necessary, he doesn't want to hurt her, and that whatever he does P will end up upset either way. He says she's not a great person, that she's stubborn and sensitive and ignores him most of the time anyway (but is that really an excuse?). It finally blew up this morning when she found out from a 3rd party that M is with me. Now she's upset with him, I'm upset with him, and he's upset that I'm upset. He says I don't understand the situation, that I don't understand the type of person P is. He also says he cares about her as a friend, and that he needs support from me during this time rather than anger.

AITA in this situation?

tl;dr: Boyfriend ignores that female friend is in love with him, doesn't tell her about me for weeks, says she's a difficult and sometimes mean person (even though he still cares about her as a friend), and ignored the whole situation because it wasn't necessary and caused drama.

being mad at BF for ignoring his friend was in love with him