False negative review left by pet owner, what do I do?

A woman I've sat for twice now left me a very positive review the first time, then a second gave a negative review containing false information, especially about the state of which the house was left in, probably out of spite from a personal disagreement we had. She is a friend of my cousin, and a personal disagreement should not have led to lying in a review, which has ultimately damaged my profile. The first time I sat for her I vacuumed her house free of charge as a courtesy, this last time however I did not. She's accused me of leaving the house a "dirty disaster" when I cleaned any bedding used, did the dishes, and left the house as it was before I started the job. When she arrived home my second time sitting and we spoke face to face she had nothing negative to say, and in fact praised me for my work and even asked if I'd be willing to sit for them again in the future. The fact that she turned around and left a very nasty review after such praise is very disappointing and frustrating.

What can I do? It will not allow me to leave a reply/response to her review, and it is damaging my image/profile as I do not have a lot of reviews to begin with. Any advice would be greatly appreciated.