The same thing happened to me.
My issue was, I didn't know she smoked until several months into the relationship.
At the start it was fine - but the problem occurs if it becomes to much and she begins to self medicate.
That's what happened to me.
My girl smoked pretty much every night. then would pass out around 11pm - and I'd carry her to bed. If she smoked earlier in the evening, sometimes she would fall asleep watching TV - then wake up around 11pm and not go to sleep until 2-3.
bear in mind we were living together and working full time.
Yes, it didn't mess with her work, but sex went out the window and it got to the point where we could not do anything without her taking her weed. We'd go away for the weekend to say Vegas - she'd bring her weed. One time she even hid it in her grnadmothers baggage (we were going away for the weekend with her grandparent, her grandparent were leavign a week earlier and driving, we were flying).
In short this will not work out. You have an issue with it - and that will not go away. People who smoke weed usually become more dependent on it. Yes, weed has not been proved to be addictive - but I believe it to physcologically so. Most of the people I know who smoke weed, become passive, have low energy and would rather sit and smoke than do something active - a generalization I know, but it's true.
I also went tha same route as you and started smoking with my GF. I figured if I were to share the experience with her, that I could somehow control the amount she smoked. Wrong. Somehow, after several months, it got to where we were smoking almost every night. I got tired of waking up every morning tired as hell.