I'm going to relate the story in a barebones, no details version because the full story is very long (I can post it later if anyone is interested.)
I had a gathering with various friends at my apartment which was very casual, bring things if you like, wear sweats, etc. At one point we decided to go to the grocery store to pick some stuff up. Problem is, one of the guests refused to leave my apartment. She lay down on my couch, bundled herself up in a blanket, and whined about not wanting to go and we should just leave her here. I flat out said, I'm not leaving you alone in my apartment. This is not a close friend of mine anymore due to a past history of bad behavior, and has in particular done untrustworthy things when left alone in someone's apartment. Saying that had no effect as she continued to insist on staying and acted offended that I wouldn't want her in my apartment unattended. I finally gave up and left her there even though I was very uncomfortable because I was worried that forcing the issue was going to ruin everyone's fun and I knew I couldn't physically force her to leave.
Other than staying home myself with her, what do you think I could have done to get a different outcome?