If she has never paid any rent and there is no tenancy agreement then she is merely a visitor who has outstayed her welcome and you would actually be entitled to simply lock her out.
It would be different if she had paid rent. This
It is often the case that a robustly worded letter from a/your solicitor threatening a court application and an application for costs, may resolve the issue without the need to go as far as court.
On your house/business insurance you may have legal expenses cover that would pay for the legal cost so it’s worthwhile checking. Some do and some don't.
Do remember that I can only give you my opinion.
Another lawyer may have a different opinion. Litigation needs at least 2 parties and neither goes to court expecting to lose.
Nonetheless, one of them does, even though they have been told by their respective legal advisers that they have a good chance of success.
If there was a black-and-white answer to every legal problem there would be no need for anything to ever proceed to court.
However I’m still of the opinion that you can simply lock her out because there is no tenancy here firstly because there is no documentation but secondly because she has never paid rent
Thank you for letting me assist you with your legal question. I am glad that I was able to help.
I am not certain whether that answers the question for you or not, but I am happy to answer any specific points arising from this.
It will be my pleasure to help you again either further with this or any future questions you have