Although we weren't dealing with Martina directly, her friend Roberta was very helpful and waited for us at the flat even though our flight was late and delayed (we did have to pay an extra fee for the inconvenience).
Overall, the flat was clean and tidy and decent sized.
It is very well situatued, particularly if you want to enjoy the Biennale, as it is 5min away both from Arsenale and the Giardini.