my sister is a bitch.

Bake your sister some 'brownies' before something really important she has to do.

 

I read this and thought it said I may try to seduce her. lol.

 

Tell her to fuck off. Seriously, if my sister tried to snitch on me to my parents when she found out I smoked, I'd have to tackle her. Try and educate her about weed, if she tries to run and tell your parents that you showed her a marijuana website just clear your history and deny deny deny. Get your little bro to help you out too. It's your words against hers that way.