Seeing that her SAT math score was 790, it is quite likely that she could get an 800 on the Math Level 2 SAT Subject Test. The percentile for an 800 is one of the lowest. It varies from year to year but was at 81st percentile in 2018. She would need to get one of the study books and take practice tests to get her speed up. My sons used Barron’s. Just keep in mind that scores on the practice tests may be a bit lower than what she would make on the real test.