Got into a huge mess with my boyfriend, and his female best friend?

[M]

Ive been with my bf for over 2 years now, and he’s a great guy. I’ve always been insecure about one of his female best friends, to the point where I told him he needs to stop talking to her. Eventually, however, I realized I was being stupid, and apologized-and they continued to talk. 2 days ago, however, I got into a twitter fight with the same female best friend. The fight ended shortly because I stopped replying to her. Following which, I told my boyfriend about it, but he said he wasn’t going to get involved because it had nothing to do with him. Nevertheless, the girl started writing more insulting things about me on her twitter even after the fight was over. I messaged my bf telling him I was hurt that he didn’t even bother to stop her. He thus went, and told her he wouldn’t tolerate hearing crap about his gf (me). As a result, they both got into a fight and stopped talking.

Now, my boyfriend feels like he has lost both his best friend, and me. I am hurt as well because he’s coming to me and grieving over her loss. I tried to be nice and comfort him, but I mean at the same time, how can I tolerate him grieving the loss of a girl who said so much crap about me? What do I do in this situation?

P.s We are all in our early 20s