You can make her do your homework, then keep lending her money, then you can make her do your homework in her underwear, then you can make her carry your books to school etc. it is a slow corruption it is not meant to be fast. You are slowly turning a nice girl into your personal sex slave that takes time.
Willpower has nothing to do with dominance the way you are talking. Dom and Sub are not in the game but will return as sexual traits.
Some scenes allow for the MC to be dominate. Katja, Igor, Petia, Anushka, Natasha, detention scene with with Feofan allows that as do a few others. but being a outcast slut blocks most of it, as no one respects a outcast slut.