Hey fellas, seasoned RP here but not perfect by any means. I'm currently in a semi-monk mode while being in a LTR and just trying to still figure out how to apply everything in it's fullest in this dynamic. I like this girl. She meets all my checklists. But she's currently breaking a boundary of mine, and has before, where if we get in a disagreement she runs to her friends house whom I also know and may even stay the night or two. Her longest was three nights. We live together. I'm not worried about some Chad in the background but I make no illusions to the possibility. Her friend is more pro-us than even her and I. Anyway, I don't like it. It's a boundary of mine that gets me every time. I've tried most everything and am somewhat currently being successful with ghosting her when she does it. My question is, if the ghosting gets her to start crawling back at what point do I act like everything is normal again. How long do I withhold all the shit they love in this scenario? I really want to break her of this habit. Thoughts?

EDIT: The friend is a girl. We've all known each other for years.