Knowing that the school was not aware of how smart your kid is, I would push harder to get her into the accelerated math class.
Some options:
1. Schedule a meeting with the principal (or AP, in our school the AP does all the class changing), the teacher in the class you want your kid to get into, and your kid. Explain during the meeting (using her current book) that she's already mastered this material.
I find that having that information coming directly from the kid is often much more convincing than the parent saying it, because school administrators often like to dismiss parents' opinions. You need to be there, but let her do most of the talking.
2. If they won't put her in the class immediately, ask for a copy of the textbook and syllabus so she can shadow the class. This way she'll be ready to switch over when they finally cave and let her in. You don't want your kid to have to play catch up.
3. Keep hammering away until you get what your kid needs. I find friendly persistence to be the best tool I have in advocating for my kids.
