I agree with bh14. I think it's time to meet with the principal.
I'm not sure what the ettiquette is about whether you need to let the teacher know that you are going to do this or not, but it would probably be a good thing to first mention to the teacher that 1) you appreciate her allowing your DD to work more in-depth, especially on open-ended projects (thank her for this modest deviation, eventhough it is clearly not enough), and 2) you are going to set up a meeting with the principal so that you can plan an educational program that will fit your DDs needs next year. By placing it in terms of "next year" you can avoid the teacher feeling defensive about the job she has done (even though she clearly should be doing something different) and, in the process of meeting for "next year" maybe something can be done during these last two months of school.
When you meet with the principal, see if your DD can come, too, and advocate for her own needs just as she tried to do with her teacher. Complement the teacher she has now for any small thing she has done to adjust the curriculum for your daughter, and emphasize that, while you know it is difficult for the curriculum to be adjusted within a class with wide-ranging abilities, you feel it must be done because of X, Y, and Z. Also, be prepared with several different versions of accommodations that you think would help. Subject acceleration and grade acceleration can be good options for schools with budget and teacher constraints, so you will probably want to familiarize yourself with the IAS and research regarding acceleration so you will know if you want this an an option.
You sound like you have a smart, brave girl!
