I highly recommend staying at Sandra's place. I plan to stay with Sandra again when I return to Geneve in a few months.
I stayed at Sandra's place for over a week, which was very pleasant and comfortable. Even though my arrival time changed unexpectedly a few times (flight delay, etc.), Sandra and her husband went out of their way to ensure I was able to check-in, welcomed, and well-taken care of. They shared lot of good tips and recommendations, which were very helpful.
In addition to Sandra's place being tidy and well-equipped, it was very quiet, peaceful, and convenient. With a little corner store (literally around the corner) and perfect cafe across the street, I had everything I needed everyday. A full grocery store was 15 minutes away on foot and everything else (e.g., old-town, CERN, etc.) was 20 minutes away by tram.