We had an awesome time staying in Elsys apartment. The place is conveniently located close to the subway and within walking distance (if you don't mind 20 minute walks) to the center or the local eat and drink area on the other side.
The apartment itself had everything we needed for our stay with four people.
Elsy helped with every question we had, offered to change the towels and even allowed us to store our luggage since we had a very late bus departure after we checked out.
All in all a totally recommendable place to stay in Santiago.