My son adores playing with the year-older girl next door, and we've had not exactly that, but something similar. Bottom line: she has learned, through school, that she is older and therefore is higher up on the playground hierarchy. If the girl next door is in school or goes to daycare, perhaps she has been "put in her place" in those places, and is simply doing the same to your daughter. That said, it still isn't nice behavior, and your daughter should be empowered to speak her piece, as well. I'm working on teaching my son to tell the neighbor that he doesn't like her behavior (and he's no angel to her, either, but in different ways, so it's fairly "even" between them) and that "I feel...when you do this..." kind of words. I also think it's 100% ok to say "this is not good behavior, and we don't do this. It's not nice" while also teaching your child to be forgiving of others' bad behavior--because, of course, I'm guessing your daughter has also misbehaved once? :) That worked well for us with a really naughty neighbor...and it's allowed my son to see clearly that T's behavior is NOT acceptable and he does NOT have to stand for it, while also not condemning him as a bad person forever. I don't think it's inappropriate for you to step in and point out to the girl that, just minutes ago, she WANTED your daughter to follow her and copy her, and that by doing a complete 180, she's not being a good friend...but if mom's there, condoning her behavior, that's hard. Depending on your relationship, you could still step in...it probably depends a lot on how much it matters to you. I would use your daughter's feelings on it to gauge how much it matters to you; kids are much better at glossing over things and not letting them matter than we think they are. It was hard for me to watch my sweet kindergartner "learn" that he was at the bottom of the playground hierarchy, but we also used that to teach him to be NICE to the kids coming up next year. Hopefully it works!