When you've deleted her she will still be able to see that you have an account, she just won't be able to see your details/photos etc.
He said his account is set to private. Like mine, I am on facebook, but no-one can find me on there because I'm hidden. I can find them and add them, but I am not visible to anyone else, unless they are on my friends list. I'm assuming this is the situation with the OP.