Changing such areas, objects, and even living beings' gravity to her will.
In her case though she only able to change her owns gravity and around her (Like a half-inch radius. Very tiny.), and her special weapons. Changing one's density to be heavier, or lighter, making her weapons or herself hit harder, or make her lighter so she can jump higher or farther, float, etc.
If she wish to change someone's else gravity, objects, and even the areas, she will have to train, thus is why another reason for her to come to this school. For now, she unable to do that until she develop it.
Will this work?