I'm guessing, but if there is some kind of eviction proceeding, the tenant is going to have legal aid come in and claim she is incapacitated, and needs a postponement. I use an eviction lawyer for my rentals, according to him, this would be a standard trick. He says one postponement is automatic, and the second with a doctor's note.
And then she might even threaten to sue you for the fall, and hopefully, if you agree to give them several months free rent, they might even drop the action. Nice of them, right??
As I said, I'm guessing, but standard operating procedure for a deadbeat.
As to whether it is a valid fall with no one watching, it reminds me of a question written on the blackboard by a philosophy professor on the first day of class, supposedly a famous Chinese philosopher wrote "if a tree in a forest fell, and no one heard and seen it fall, did it actually fall"??
It was too many year ago, but the answer to it is YES. In your case though, your tenant, it could very well be a staged fall where she'll have to prove her case. It might stretch out eviction processing, which may amount to the same thing.

