She was at a National Trust type place which had a second hand book section. As she was browsing she found £165 hidden in one of the books. Rather than hand it in she just kept it and looked rather shocked when I said it was theft.
My perspective - the book belonged to the shop and therefore so does the money.
Her perspective - just luck she came across it so decided to keep it/the shop should have checked the books.
Just for extra info, she doesn't struggle with money but does live payday to payday.