Thanks for the tip Fred. I did in fact give it my best shot, and showed at great length that it was just a scam, and that the 7 photos submitted by her did not even show any lack of cleanliness, except for one showing a couple of fingers with a tuft of hair allegedly taken from the shower drain. Considering that all the other allegations were clearly unsubstantiated, the small tuft of hair could easily have been from one of the guests themselves after having taken a shower the previous day.
Despite my exposing the guest airbnb refused to listen and has insisted as judge and jury to reimburse hundreds of euros back to the guest.
After a 3 year honeymoon with ABB when I had no problems at all with all the other guests, this has now changed everything. I was naive not to realise there are such scam artists out there, and that they would plan the whole thing to trap you. Because of those few I will have to take all the precautions with all guests and take nothing for granted. I suppose it is like locking your car. 98% of persons passing by would never think of stealing it or something in it, but you need to keep locked at all times to protect yourself from the other 1 or 2%. Sad really, but that is the reality.