Ours is this way, too. She has very high standards for herself and probably does more than she has to. She was upset with her Iowa Assessment scores (used to be Iowa Test of Basic Skills) because she felt the percentages she got weren't up to her standards. They were just fine and probably better than 97% of her classmates. I think yours is the same way where she is already thinking ahead to college/vet school and has heard many times about how you have to have good grades to get in.
ITBS isn't everything. I scored 99th percentile every year, but didn't even graduate in the top half of my high school class, and flunked out of college. I had a 31 ACT too.
I make sure my daughter does her homework every night. Now I no longer have to make sure, because she does it on her own without prodding. I'm very proud of her for this, because she seemingly got every physical and personality trait from me.
In retrospect, I had terrible (none) homework habits. I had little interest in doing it, no incentive to do it when I could still pass my class by getting zero on my homework and 100% on every test, and that killed me when I got to college. I could no longer rely on knowing everything on the course syllabus before the first day of class. It didn't help that my gender dysphoria was kicking my ass harder at this point than at any other time in my life, and I was really only there because I wanted to play football.