I've homeschooled three girls now. Youngest is 16 and the older two are college grads. All probably gifted, one highly gifted and always significantly advanced in academics.
IME, age 8 is when things start changing for girls in the brain in preparation for puberty. In all three of mine, there were definitely changes in attitude, though presented in various ways according to personality and other factors. I thought I was the most awesome mom up to that point, haha.
One thing with gifted kids...the rate of progression in academics can be significantly faster in the early years when they are more compliant and it's all a bit of a novelty. That does change with the brain taking on new tasks, and that's okay. If the kids are way ahead at this point, you've got some room to step back and relax and let other growing occur.
You sound like an awesome teacher. That said, it may play out that your daughter responds better to other input. Maybe not, but that's my experience, and I've learned not to take the rejection personally, because it's developmentally appropriate. An example from our life: I am a pro photographer. Yesterday, my daughter started a photography class with another local photographer. She will learn more from him because she will be more receptive, though I can reinforce lessons at home.
Good luck. I always say that by the time we figure all of this out, the kids are grown and gone and we have all this useless knowledge about child rearing.