Hey Ents, need some advice

So I've never smoked, never really had friends that did, never felt a desire to. However my girlfriend told me a few weeks ago that she smokes up semi-regularly to help chill out before going to bed sometimes. She's been hiding it from me for months because she thought I would judge her.

But here's the deal. I don't care, but I can tell she's still nervous about it and still tries to hide it when she does. We're moving in together in a month, and I'd like some advice on how to be a good boyfriend and roommate to keep her from freaking out.