Do you have a sponsor? What does she say?
I think, if it were me, my sponsor would probably say, focus on my own side of the street, stay sober and do an inventory on it to figure out where my character defects might have come into play. Id also pray on it that I can do God's will, and not my own, and I'd try to get rid of that resentment. You know, your daughter is an adult and a mother of two. She is likely to want to make decisions about her boyfriend staying over for herself. Maybe your rule is no boyfriends staying over, and now she's realised that you do actually MEAN that, and has decided to like somewhere that she can make those decisions for herself. That's the kind of decision people make every day, and there's no reason really to take it personally. Why wouldn't she want some autonomy over her own life. What's the alternative, living with her mother for the next ten years?
Maybe she'll find her own place, or maybe she'll come back eventually. Who knows. Sounds like her staying at a friends until everything has cooled down could be a good thing. If she moved back tomorrow would you be willing to meet her halfway on the household rules that are causing conflict? If not, which is fair enough as it's your home, then be prepared for her moving out. I don't know anyone whose landlord has the say over whether their boyfriend stays over or not.