The flat is simple yet comfortable, has everything one would need for even a longer stay.
Its location is amazing, 2 min from the airport, a minute (8-10 walking minutes), from Oriente station, from where one can take the metro or a bus to anywhere in Lisbon or even a train or a bus to anywhere in Portugal (and Spain). There's also the shopping mall with a supermarket and the other usual shops just by the station.
I didn't personally met Katia, but she was always available via messaging and has been very helpful.
All in all it was a very good experience, and I recommend the place.