I'm sure that other people will chime in soon but a couple things come to mind. First, does your district have a gt department? You may want to call them and see if they could participate in your meeting or at least provide guidance re the politics of gifted at your school.
Second, I would start collecting "data." Bring in test scores, the types of books that she is reading independently, samples of writing, samples of math work and anything else that supports your assertion that your child is advanced. You may want to call your contact back and ask her what the school would like to see.
Finally, go in there with some humility. You might want to say that you know everyone thinks their kids is advanced but here is what you are seeing. Ask for their opinion and acknowledge their expertise. Demonstrate that you want to be a team player with the school.
Good luck.
