I would too...but that's just me. If his other female friends don't bother you but this one does...because of the history between them, what would it hurt for him to cool it with her? I assume he still has other people that he can be friends with.

The important thing to me is how this friendship with her makes you feel and sounds like you're not feeling to sporty about it. It would be a kind gesture on his part to distance himself from her.

I would be careful though about making this request very often because it could be interpreted as just plain old jealousy.

Best wishes with all this