Actually, that theorizing is probably what actually happened. If you think back to the scene in Flesh and Stone where the Doctor leaves Amy in the forest - and then reappears a few seconds later. Not only is he wearing a jacket (which we SAW him leave with the stone angels earlier) his whole manner is different and he's telling Amy to remember what he told her when she was seven. The theory is that Eleven from the near future is crossing his own timeline in order to fix things. And also (I think I pointed this out in my review as well) there's that scene in The Eleventh Hour where Amelia is sitting in the garden on her suitcase; it's morning, she hears the sound of the TARDIS, looks up and smiles - and then we cut to grown up Amy waking up as if from a dream. But - perhaps it wasn't and the Doctor DID go back and tell Amelia something that she now needs to remember.

It still doesn't explain why she thinks he tells her everything though.