Let me ask you this, Mr.Gray. What would it have hurt to leave the house and go somewhere else? Worst case scenario, the demon keeps fucking with them, right? Nothing lost. Well, until the stabbing starts, anyway.
So it was worth doing. Also, I think it would have been worth getting some more people involved. Some friends, assuming they had more than the one. Get a half dozen friends over, they can chill and hang out in your bedroom while you two get some much needed sleep. If Kate Hulks out then there's enough people there to wrestle her to the ground or whatever. Not ideal, no, but if they could have gotten a couple nights' sleep with no problems maybe the demon would have chillaxed. Again, worth trying in my mind.