...at age 9, she has to take a bit of responsibility for communicating and advocating for herself. ... There is a certain mistrust if it all comes from the parents. You should prepare your DD to at least confirm what you are saying since it is likely that the administrators and counselors will want to speak to her directly.
Agreed 100%. I've had this talk with my daughter (turned 10 a few weeks ago) many times. She had a very difficult year with a math teacher last year. The situation may have improved if DD had stood up to the teacher. She's in a ne school this year, and she's trying, which is great. I know this process isn't easy for a child, especially a child who isn't a natural wavemaker, and I tell her that I understand it's hard for her. I worked with my daughter by getting her to think about what she could say (even practicing saying a few things).
I'll also add that in my experience, the best successes with my kids are with the teachers/administrators who listened and acted the first time DH and I brought something up. Unfortunately, many educators are basically ignorant about giftedness and we've often encountered so-called "education professionals" who honestly seem hostile to giftedness. It amazes me that people can be so clueless about an important part of their own fields and yet still call themselves experts. In my experience, the best solution is to avoid them.
In your situation, what's the fifth grade teacher like? How will your other child do with a younger sibling in her class? My DD10 is ahead of my DS12 in math, but he seems to handle it well --- primarily, I think because his main talent is in another area in which she doesn't excel the way that he does.