Part of the problem will be that your daughter is only part time. We see it all the time in our daycares where a child that is not there all the time tries to become part of the group and the group is used to doing things a certain way and not as keen on including new people.

It is common for children to feel posessive of things they have been playing with all week and there are more sharing issues when a child is part time and others are full time.

Not saying that the behaviours being shown aren't out of proportion and that something doesn't need to be done so far haven't seen anyone pick up on the fact the girls aren't together everyday. One belongs more so to speak or at least feels more entitled as on the other days things to do belong to them.