We know of at least one missing scene between the Doctor and Amelia during which he told her at least one very important thing

Yes, and I'm hoping that that is going to explain a LOT! I'm also starting to wonder if there have been other meetings which have somehow been erased from one or both of their memories.

Since Amy's smugness and arrogance are beginning to really gall me, this is about the only explanation that has any appeal for me. Because Amy as we are seeing her now is claiming a status with the Doctor that appears to be based on nothing but an inflated sense of her own attractiveness.

I rarely do this - but WORD!