Need Evidence ?

One day an old woman walked into a shop and got some dog food, she went to pay for it and the cashier said
"you can't buy that dog food we need evidence that you have a dog",
so she bought in her dog and she got the dog food.

The next day the same old lady went to get some cat food and the cashier said
"you can't have that cat food we need evidence that you have a cat",
so she went home and got her cat and she got the cat food.

Next day the same old lady went in again and she had a box, she told the cashier to put her finger in it, so she did. She said it felt warm and soft, the little old lady then said now you're satisfied can I have some toilet paper please!