“To have fun with her” means that they made fun of her and laughed at her.
Here in the story, Wanda is a source of amusement for other students like Peggy and Maddie because she is different from them.
They deride this because Wanda never fights back.
That’s why she make a source of amusement.
Final Answer:- Because of her never back answer she was made a part of enjoyment of others. Some of the adamanty students like Peggy and Maddie always mock her appearance.