When I was in school, girls would say something like, 'I know something about you, but I'm not telling you.'
Now, it's extremely unlikely that another person, especially a child, would know anything about you that you didn't know yourself.
Also if they really did know something about you and they didn't like you, they would shout it from the rooftops.
I often get the feeling that Drisgirl doesn't like me much and I don't think I'll be invited around for tea anytime soon. So if she did know something about me I'm sure that you would all have heard by now.
So rest assured there isn't anything that she knows.