Sounds like you did the right thing. Of course these parents are going to be ice cold toward you. Nothing there child does is ever wrong. I was just going to say that you should just write these people off as lost causes.

However, the sad thing is that your child has to deal with their child. You can ignore those adults, but your child has to deal with being near this other child. That means there is no easy solution. But if this kid is as nasty as you describe, and I'm inclined to believe she is, then your daughter probably needs to just avoid her as much as she can. This kid is not going to be well liked by other kids. She and your daughter will someday travel in different circles. Until then, you might try to support your child in building a circle of friends that might not include this mean girl.