She wasnt Invited and the op did the right thing by not making a fuss, it was her nebor that is out of line.
No I hope that her label falls off as in she grows up and stops acting like a brat, but then again how is she going to learn to act non-bratty ????
Plus 11 is around the age of social reasoning, she might be delayed because of her home life.
AGE OF REASON AND FRIENDS
The age of reason is also an age of cooperation. Children from 7 to 11 years old move away from pre-school romance and feel the need to define their sexual identity. In fact, during this period, girls and boys play less together in the schoolyard and both groups have distinct activities.
It is also during that period that the child will understand the advantages of playing by the rules, respecting others and cooperating through spontaneous group games and teamwork in the classroom. Friendships are often stormy at that age because children are changing a lot in very little time.
I'm not saying op should have invited her, unless her dd or sister wanted her there.