What would you do?

Princess Belle has this friend that has LICE!  Now I don't really like this girl anyway, she is kind of a brat and always likes to get the other kids in trouble.  And her mother doesn't  treat the lice!  I HATE lice.  They are gross and creepy and make me itchy to think about them.  I found this out after Princess Belle has spent all day Saturday playing with her.

So, I treated all my kids, washed their blankets and toys and treated our house like we were infected just to be on the safe side.

But from here on out, what you do?  I have told Princess Belle I don't want her playing with this little girl.  Princess Belle has other friends she plays with, so she doesn't mind.  I also reminded Princess Belle about the rules, no sharing hats and brushes, no putting your head up against other kids heads if you can help it.

Am I out of line to ask Princess Belle not to play with this other girl?

Update: it isn't working anyway, I just looked out and they were playing together, and I am too soft-hearted to enforce it when she looks at me and asks if she can play with Princess Belle.  But on the bright side, another little girl who was out with them said that her mom took the other girl inside her house and treated her, so that is something.