Me (A) and B have a mutual friend C who we've both known for a few years. Until recently both me and B were better friends with C than we were with each other. C has moaned and bitched about B to me quite a few times over the years. I tend to either ignore this or remind C that B is supposed to be her friend. B knows that C does this and still maintains that C is one of her closest friends.
Naively, for a long time it didn't cross my mind that C might also bitch about me behind my back but she does. I've started to distance myself from C and am on the verge of ending the friendship. Although she has some good qualities, I dislike the two-facedness of her talking both behind my back and B's back. This has caused some tension in my friendship with B as she can't understand why I won't just accept it as part of C's character. So I'm curious about what others would do in this situation.