Most of these replies are in the same vane, but it could just be that this client is on the bones of her backside skint.
Has she ever behaved this way before?
Most customers want them nice and clean for Christmas, she may have problems that's she's too embarrassed to talk about.
You could dump her, but what if she gets another window cleaner? He could be a lot cheaper than you and then you may lose a few of her neighbours too.
My first reaction would be to dump her too, but in this economic climate I may wish to give it more thought.