How do you feel about your friend(s) talking to people who have bullied/isolated you?

I understand that at work you have no choice but to be diplomatic.
...but like... I walk in today and my only friend is talking to the girl who has successfully almost isolated me. I got very uncomfortable so I didn't stop to say hi. But my friend didn't stop the conversation to greet me either.

This, versus when I'm speaking to one of this bully's friends and this bully walks in, her friends will even cut me off to greet her and start their own conversation.

I'm thinking maybe I should distance myself from my one and only remaining friend as well. It's the tiniest things that bother me. Because the bully used these tiny methods to begin with, taking everyone's attention, cutting me off, pretending I don't exist, etc.