@Joanne-Elizabeth0 if there are only 2 nights left then it's not really worth the hassle of kicking her out and risking a bad review. I'm also not sure what your reasoning could be for kicking her out, as there is nothing in your listing or in your house rules that forbids outside guests/visitors. If you charge more for 2 guests rather than 1 you could always request the additional guest fee from her for the times he has been staying.
I'd suggest updating your house rules to make it clear that no outside guests are welcome. I've updated mine to say no visitors after some issues with guests. I have had one or two guests since invite outside guests over, but when I message them with the house rules and tell them if they break the rules again they will be asked to leave they start behaving themselves.