People don't need durgs. It's a lifestyle choice. Since you don't approve of her lifestyle choice, that means you both have a slightly different set of values.

I could imagine things could get pretty weird between a pot smoking gurl and a non-smoking guy every once in a while... when people don't see eye-to-eye on something, anything, it could be a problem for a relationship. Especially when it's values that you don't see eye-to-eye on, if you feel me here.

Why don't you tell her your feelings, brah? Show her this post, even. Tell her your feelings about it, and listen to her feelings about it too. Be sure and understand each others' feelings on this, understanding is the most important issue in relationships.