When your mum is still making you food on demand at 18 years of age, I think it's safe to say she may well be somewhat protective. My mum loves me dearly, but if I said to her mum make me a sandwich please, I'm sure she'd say you have legs don't you? You need to show you're independent and can succeed in life even when smoking cannabis. However, if your parents demand you stop, unless you plan on moving out of home I suggest you do what they say. It is their home and their rules after all. I like how you approached your mum about not emptying your pockets though. I think you're right it would have just embarrassed you both and made things worse, so good on you.