While not married, I’ve been in a serious relationship with my last partner who knew I stuttered and my current partner now. With my last partner I was more fluent and I generally felt more at ease as long as I wasn’t forced to order food, talk in front of too many others or the like. My (now) ex was always positive, patient and super helpful. The same is true of my current partner, although my disfluency usually makes me have to use apps to help slow my speech or type what I want to say on my phone. Dealing with disfluency is a really tough challenge. However if the mannerisms your partner displays are enough to make you uncomfortable, you should let them know. I think you should let your girlfriend knows there will be better days and harder days. Any loving partner should accept and get behind that. After all, we’re much more than our stutter.