My daughter who is about to turn 13 has been friends with a neighbor girl, 11, for about 4 years.  This girl is a lot of fun and very outgoing.  The problem is that when her brother, 15, is around, if he says something derogatory about my daughter, she will go along with it instead of being loyal to my daughter and taking her side.  This neighbor girl seems to not understand loyalty and tends to go along with whoever she happens to be with at the time.  Once, on purpose, this girl kicked my daughter's ball all the way down the street and it went around the corner and she refused to go get it.  Tonight this neighbor girl, her brother, and a few other kids were outside playing at 9:45.  My daughter heard them and was looking out the window.  Then the kids started talking about her saying my daughter was spying on them, as if there was something wrong with her looking out of her own window.  I went outside to speak to the kids, and the older brother said, "Well, she looked out her window 8 times."  I told him it's her window, she can look out of her window if she wants, and told him to stop looking at her window.  These are just a couple of examples.  Am I being too sensitive or is it time to encourage my daughter not to be friends with this girl anymore?