Third grade is when mean girl behavior really starts. I have had two phone calls from parents where my daughter has been out of line (or perceived to be out of line: in the first instance she was, the second instance she was just being tactless). In both cases I used it as a teachable moment after determining what happened. I was at the mercy of mean girls when I was in elementary and it was really really horrible, so I have told my daughter that she will not be a mean girl, period.
The school may have been the ones to suggest the time slots solution. When my daughter had a problem where she wanted to play with one girl (her bestie) but did not want to play with a third girl too (who was nice but hogged a lot of the attention), this is what the teacher suggested. Eventually my daughter got sick of time slots and made friends with the third girl and now all five girls in the group play together. So the time slot may be coming from the school. But in your situation, I agree with longcut, it's a good time to teach her diplomacy skills (rather than doormat skills). At least she understands that being popular isn't all it's cracked up to be -at that age, that's all anybody wanted to be (if they weren't) and but the truth is you just need a good group of friends (or one). This is what I keep trying to teach my daughter.
