I will try not to rant, here are the facts.
I have 2 girl friends P & M. They are very friendly with each other and see each other regularly. I'm more friendly with P, see her daily-ish & see M fortnightly.
M has a boyfriend of several years called B.
7 months ago friend P kissed boy B. B and P both confirm that it was only kissing, but they did share a bed. They also shared a bed a few months later, but apparently didn't even kiss.
Friend M does not know about the bed sharing or kissing and in those 7 months friend P has continued to be just as friendly with M.
Fast forward to now and I now know about the kissing. I am very cross with P and B for putting me in this position as I feel M should know. It's also likely lots of other mutual friends know, so M is bound to find out IMO. They obviously don't want to tell her as it was 7 months ago, 'meant nothing' etc.
At the very least I feel friend P should stop being so friendly with friend M and I feel it's adding insult to injury. Friend P says, "I don't think it's bad to be her friend and it's not taking the piss out of her." she would also "like to pretend like nothing happened and move on - as [she has] done for 7 months."
AIBU in thinking it is shit:
1)of both P and B to even be kissing
2)for friend P to continue to be nicey nicey to M.
btw we're all 28ish, no children involved and friend P has kissed other boys when out who have GFs