[sten]

they should have cameras showing the drop off. at that point, it's on their property and it's their responsibility, regardless of some sign on the door. otherwise, any criminal group could just start jacking cars in rental lots knowing the company doesn't care since they'll get money from the customers insurance company

meanwhile, the rental company should have insurance against theft on their own property.

it's up to them to secure their own lot.

[Still Thinking]

Assuming she actually dropped it off. Several posters have made the point she could have wrecked it or kept it and just returned the keys.