dude, dont sweat it. your mother will always be your mother and you will always be her son. nothing you do will ever change that and she knows it just as well as you do.

now that she knows you smoke, do what i did and take advantage of the situation and EDUCATE HER on the truth about hemp (do your research first so you dont sound like you're just pulling shit out of your ass). if my experience is anything to go on, she will eventually become less and less against you smoking it, or she will at least resign herself to the fact that there's nothing she can do about it. you just need to keep at it and find excuses to bring it up. the more you talk about it, the more comfortable she will be talking about it with you.