My sister is an obsessive perfectionist, what do i to help her?

My older sister, is the genius of the family. People are always telling mom that she is going to do something great in life, mys ister is wierd. If she doesn't get a 100 she thinks its not worth it. I swear its like this, she gota 98 in her last midterm, she threw away the paper and locked herself and studied for five hours straight because she didn't get a 100. she is always saying if its not 100, its not perfect.