Just thought I'd share a response I posted to another thread about similar concerns:
Originally Posted by nycindie
. . . Now, about relating to all your mutual friends. I have been a part of several large circles of friends and acquaintances in the past. Both these groups saw lots of dating amongst each other going on.
. . . Personally, I had a few relationships in these circles that ended and I saw that instinctively I wanted to isolate myself from the pack to deal with it. But not hiding out helped immensely!! I still showed up to social events and get-togethers -- why be the one who's curled in a corner crying? -- and I reminded myself that I had every right to be out and about with them as he did. I had friends I wanted to stay in touch with. It's so easy to think that a group will follow conventional stupidity and take sides when a couple in their midst breaks up, but you can make sure you don't present an attitude that would be ripe for that happening.
I just held my held high, whether I felt I did something wrong in the relationship to bring about its end or not, and I talked about it to the people with whom I felt safe, until it could be acknowledged more openly among everyone. I talked about my feelings, without wanting to turn anyone against my new ex, but just to be heard. If you're careful not to trash someone after they break up with you, all your friends will likely be able to be supportive of both of you. Give yourself enough private time to mourn the relationship, too, and it won't be as hard to face all your mutual friends out in the open.
But go out and socialize with everyone just for the sake of getting out and being in the company of people you like. You don't have to talk abut it if you don't feel like it, either, and you can say so if someone asks what happened and you're not ready to answer. Just take care of yourself, whether you're alone or in a crowd.
Maybe this would be helpful. Anyone who chooses sides would seem to me to be rather immature, anyway, unless there was a reason, like one person was abusive or something.