Oh dear, oh dear! This would make a really good question on a law exam paper, and the answers so far have covered most of the bases. You would have to discuss the extent to which a parent is responsible for the actions of their children, the difference between actus reus and mens rea, you would have to go into contract law with particular reference to shops - when is the contract of sale made (I seem to remember there was a case involving Boots the chemist back in the 50s which held that it is made at the checkout), and also that it is the shopkeeper who has the final say on whether there is a sale or not. You would dismiss as irrelevant the fact that the lady was pregnant, and also that she was thrown out (I assume not physically) of the shop - any shopkeeper has the right to refuse to serve anybody for any reason - or indeed for no reason. Like I say, not by any means straightforward.