Is there any way you can have her do advanced reading? Maybe she is bored and thinks its stupid that she has homework thats to easy? Try letting her choose a book and see if her interest stays. You can preface it by asking if she has any problems with the class reading. If she doesnt, skip the class homework and let her read what she wants.

I have a good friend whose sister nearly failed because she has problems with doing repetitious homework. If you challenge her now she could potentially get into an advanced class where the material will hopefully spark her interest and keep her engaged.