[The One and Only...]

Say, "When I lead the revolution, your death will be quick and painless."

That should get her to leave you alone.

OR...

When she brings up relationships in general, you might want to say something that hints you want to be alone.

Example:

Girl: "Why don't you have a girlfriend?"
You: "I'm sort of enjoying being single. I don't really want one right now."

That way, you're being general rather than targeting her specifically.