@Simone466 Yes, I know, that is always in our minds isn't it?! Its almost as if we are held hostage to a degree, scared to death of offending guests by asking them to follow the rules clearly laid out!
I don't know what you can do about it, other than having AirBnb to have them leave. What an awkward sitaution, whatever happens, as you're stressed and they seem to have no morals, thinking it's perfectly fine to lie and take advantage of others.
I don't see how you can prevent them from leaving a negative review, other than having AirBnb force them to leave and then trying to go through the process of preventing them from reviewing, or getting the review removed afterwards. I am still pretty new, so I have not had this sort of experience and maybe some of the more experienced hosts can weigh in, but from what I understand, it is pretty difficult to get reviews removed.