Relationship/lifestyle question

My girlfriend told me tonight she wanted to go get high with some friends (she has an addictive history-just not with drugs) and I reminded her how I felt about drugs and how I didn't want my girlfriend to have that lifestyle, especially since her choices reflect on me and vice versa. I told her I would be upset if she did it and how I would respect her opinion if she didn't want me doing something. But she went out and got high anyways and texted me about it like an hour later. And then she tells me a guy grabbed her butt who I have asked her to hang around less because he is always trying to/succeeding in touch her inappropriately when I'm not around. It makes me so frustrated. I don't know how I should feel I'm just upset and mad and frustrated. What would you do in this situation??