Welcome JoAnnQN,
Great to have you here. I think that age 9 and 7 are young enough that you should see wonderful growth this year and perhaps reverse some of that underachievement.
If you daughter is an audio learner, you might try some of the audio programs from 'The teaching company' or some audio books that are high school level, just to wake her up to the idea that there is a whole world out there. My son, age 12, just listened to Obama's 'Dreams of my Father' and I'm not sure how much he got out of it, but I know that he got farther with the audio, and us stopping the program for me to explain the references, than he would have reading silently.
Do you have any summer programs locally that are meant for gifted learners?
Smiles,
Grinity