It means she wants to be together with you, either as your girlfriend or for sex.

I see, It's a rather interesting question.

It means she wants to shag you senseless!

(I realized my answer was wrong)

Hi, we say "She's all over you like a rash." It means that she won't leave you alone and can be insincere towards you as well. Example: A. Let's leave the party right now. B. Why? A. I don't want to run into Miss X. She's all over you and won't leave me alone.