My experience with Petra was more than happy, her apartment has a big clean living room + dining room, and the bedroom is vey comfortable,her kitchen has all the thing you need.
Petra is a wonderful host, in her apartment she's prepared all kind of tips of Mexico City, from what to look to what to eat. She even prepared a printed guide for my trip to the pyramid.
I'll definitely stay with Petra, if I visit Mexico City again.