My little sister stresses herself out over school the point of nausea?

My sister is 12. She always hated school and every Sunday she worries about school to the point she cries and is in a sad mood all day. She cries about her homework sometimes that she can’t get it right. She gets so crazy over it. She’s constantly checking her backpack, she never leaves any books in her desk at school so they’re always in her backpack and it’s so full of books she doesn’t even need, she goes the extra mile to carry a heavy ass backpack every day. I believe she has some sort of OCD. Tonight she’s been crying, not wanting to eat and was dry heaving because of school and she was stressed about not knowing how to draw arms and legs on people. She wouldn’t be stressed about not knowing how to draw if she didn’t have school the next day. My parents are not taking this seriously AT ALL. they know she shouldn’t be this way but they aren’t taking any steps to try to fix it. She’s my sister, I love her I hate seeing her be this way, she’s a kid she shouldn’t be this way. Any advice on what I should do?