I want to avoid the girl I went to homecoming with
Why do you want to avoid her?
I don't want to see a girl who dresses up like a clown
If you don't like how she dressed let her know. Just avoiding her and not telling her is a really mean thing to do to someone.
I'm afraid of how she will react when she sees me. I just really don't like her.
You should try and be more honest with people about how you feel. They will come to respect you for it. You don't have to do it in a mean way, there are lots of ways to talk to someone.