Hey man i had the same prob about 10 months ago dude, i was dealling a dope here and there ya know nothing big just a few O's a week, mum pulled half an ounce outta a bag i had in my room so my lill bro could use the bag. Made her so sad man, crying and shit i actually wished she had just got reall mad instead, its such a shit feeling aye.
Well if ur gonna keep her happy (and u should, she's ur mumma) stop it or dont do it at home where she can find it only advice i know man :l good luck dude