Unfortunately, this absolutely happens, and it is incredibly disheartening when it hits a perfect 5.0 track record. Running my property for the last 7 years, I have had similar situations happen once in a while, and honestly, it is tough because it feels like there is no clear way to solve this issue permanently.
When a guest leaves an early check-out after a dispute or a denied refund, they almost always use the review system as a weapon to retaliate.
Your best path forward right now is to contact Airbnb Support immediately and state that the review violates their Reviews Policy regarding extortion or retaliation. If you have written chat logs on the app proving she only made these claims
after you declined her refund request, Airbnb will sometimes agree to remove it. If they refuse to take it down, make sure to write a calm, factual, professional public response to her review so future guests can see your side of the story! Hang in there.