I think most of us feel that we would have been embarrassed about it if it had been an accident, whereas she wasn't at all. That is what makes us feel it was deliberate.
Hubby asked me who sat down first and I had to think, but I seem to think that I was there first and she came a bit later.
I did wonder about the assortment of things that she would end up with if she did this often, but they usually put the receipt in the bag unless you ask otherwise and she could have taken the items back to get the money I suppose. She would have had to get round the fact that payment might have been made with a card, in which case they would insist on the card for the refund. But if she did that often surely they would have started to recognise her?
Maybe it was totally innocent and she was on tranquilisers or something.