K.,
What a good opportunity to teach your child about respecting others and how to speak to people. In my opinion, your family is responsible for setting boundaries in your house and with what is acceptable behavior around you. Let your child know if someone is not being nice to her or someone else in her presence, how she can stand up and say "I don't like that when you are not nice...or That wasn't nice". As the adult, you have an opportunity to lead by example. If the friends child is not behaving, you could say, ex: Susie, that wasn't very nice, why would you talk to someone who is your friend, or mother, who takes such good care of you and loves you so much." You get the drift. I think it is fine if Mom is not going to correct the child, for you to set boundaries in your home and around your child. You child will follow your example. You could always speak to your child afterwards and explain that it just wasn't nice. If this fails to help the situation, you may have to back off of the friendship for a bit, but, your daughter will have to learn in life to work with difficult personalities. Maybe you could take the kids on some kind of volunteer mission or get them involved in some kind of service to others project as a humbling experience with those less fortunate, such as cleaning up old toys to take to a shelter, or putting together a basket to donate to a shelter for women and children. Often the women go to those with children and with nothing. Good opportunity to think about others. Just an idea. An experience may leave more of an impression than words. You could even come up with an experiment to say 3 nice thing to everyone you come in contact with for a week. The idea being to change the focus from negative to positive. Then get together and share the experiences and reactions of others. Works with kids and adults. Of course adults may want to try it for longer. Good luck.