You've stated that you've been with your GF for 4 yrs. Then5 months into it you both got serious. You asked her to stop & she asked you to stop.
So what I read here is that you've both been clean for over 3 yrs??? Is this correct?
For some people an addiction never fully goes away. I have a family member who's been clean of H for 12 yrs & craves it every day.
If her soul reason to stop is just based on you....I see resentment rearing its head in the future. Your GF needs to stop for herself & no one else.