Answer:
She need to set a experiment with those variables:
Performing best on test.
Getting more sleep.
Step-by-step explanation:
So, in order to prove her hypothesis she need to perform on tests taking those more sleep sessions and see her results.
After that, she need to perform tests without taking thous sleep sessions before, and see her results.
At the end, through comparison, she will be able to prove is her hypothesis was correct or not.