How should I go about telling this girl I know she is avoiding me?

Ok, so I recently met this girl and me and her have hit it off great or so I thought. She told me she has never had as much in common with another guy before and she just kept saying things that made it seem like she felt strongly for me like I did for her. Anyway we talked late last night and then went to bed. Now today she came on her yahoo and suddenly she signed off. Now I see it says she is connected with someone which means shes on and just doesn't want her name showing up to chat. I honestly have no idea what happened as I don't think either of us said anything wrong. If she ims how should I go about telling her I know?