Do you have any above-level testing to use for advocacy? Does your district use any insta-quick-testing thing like the STAR test? If they haven't given her ANY above-level testing, that would be my first request. Demonstrating ability on tests gives you something solid to use for advocating.

The only times we've had good math accommodations in a single-grade (not split level) elementary class was the year DD was allowed to work at her own pace from a higher-grade textbook. She was given pretests and skipped anything she could already do. She finished about half a grade of math in just under 3 months--and then, alas, the school year ended.

If the math is something she finishes quickly and has extra time, you could ask for enrichment such as Dreambox or Beast Academy Online--they're both decent for building concepts which will expand her depth of understanding. The Beast Academy textbooks are also really spectacular if paper books would go over better. If I had to choose between greater depth and greater speed, I honestly would go for depth--I think it will make a bigger impact on her learning in the long run.

For language, maybe it would be possible to have her join an older grade class for some lessons? The school may be reluctant to do this for scheduling reasons, though--teachers often just stick in lessons where they have time, and every class has a different specialist schedule so the time of a subject might change from day to day.