@Whitney172
As to my own situation, I called Airbnb and told them I wanted them to ask this guest to leave because she was complaining about something (the noise from a bathroom fan) and insisting I have it fixed, but actually there was nothing wrong with the fan and that I wasn't going to spend hundreds of pounds on an electrician to fix something that was fine and had caused no problem to the hundreds of other guests. The rep thought that was completely reasonable.
What I didn't explain was that the fan issue was simply the straw that broke the camel's back. The guest had been problematic from the very start. She had been staying for a month by this point and I'd had enough of her harassment (and it was harassment - she was sending me nasty messages at 3 or 4am).
However, two things happened. Firstly, the rep told me the guest had contacted Airbnb a week ago to complain about something (the exact moment that I had told her she couldn't have another person 'move in' to her room and 'split the rent'). They wouldn't tell me what it was, but as they never contacted me, nor opened any case, I assume they realised too that she was irrational and unhinged.
Secondly, the rep checked the message thread. This is why it's SO important to have everything documented in the Airbnb messaging system. They always check this before doing anything. From there, the rep could see all the crazy messages from the guest and the problems I'd had with her previously, including something about a condom and unauthorised overnight guest. This was deemed as totally unacceptable and the rep agreed to contact the guest and ask her to leave.
I offered to refund her the remaining unspent nights. The rep told me that was kind of me, and that I didn't need to do so, but I didn't want some lengthy case, which no doubt could drag out until the end of her stay. I just needed her out of my house and out of my life. She left willingly. I don't think she was expecting me to offer a refund, which is probably why she tried to make up some sort of bogus complaint.
To be honest, this guest shot herself in the foot. My messages to her were polite, professional and calm at all times. Her messages to me became increasingly bizarre, hysterical and personal.