If the math instruction is based on common core, she should receive grades based on whether she is able to demonstrate knowledge and
Skills related to the common core standards. At least in schools I’ve worked in, the report cards reflect whether or not standards are met in specific areas and aren’t based on test scores at the elementary level. Therefore, even if she fails the test, if she can show that she has the knowledge in other ways- that should be the important thing for her grades.
Secondly, if you find that she is needing significant accommodations, you can look into requesting that your school consider a 504 plan which allows for accommodations for students with medical or physical impairments such as adhd or anxiety. If she qualifies for a 504 plan, the teacher would be required to provide accommodations to her- such as less items per page, a separate location for test taking, extra time on the test, or other things like that that could help reduce her anxiety.