I'm assuming you've already tried talking to her, and it didn't work... either that, or you know she won't listen.
In that case, IMHO, all you can realistically do is try and distance yourself from her. By this I mean, spending more time with other people in the group... but remaining civil to her when you have to interact.
By being civil, even if you don't like the person, you're still polite enough to her when you have to interact with her (in most cases, it's more for the benefit of other people in the group, so this way, they don't need to feel awkward or have to take sides, as you said).
Typically, it's a gradual process that would need to be done over a few weeks (if not months). Obviously it depends on how close you are / were, but if you dropped her like a hot potato, it's bound to cause ripples in the group. Although it should be feasible if your group is large enough.