I don't know whether other schools will allow this . . .

DS7 in 1st grade was so far ahead in math that they allow him to do math on the computer using a self-paced program called successmaker. (He still has to do the 1st grade homework and take the 1st grade tests). Perhaps a little self-paced work at her level would do the trick? I know how hard it is to get your mind around skipping into a grade where the child is 3 years younger than her peers.