I would upgrade to a 20-gallon, just to give her a little room to stretch. I have five sand boas, and only one will ever be found above the substrate (the male I told you about. He still likes to sit ontop of his hides sometimes and test the screen, but it's nowhere near as bad as before.
Also, ditch the sand. I tried it with my snakes and they kept getting it in clumps under their lips, even though I fed outside the enclosure. Also it's dusty and unnatural for them, as they live in a sort of scrubland with clay and dirt, not a whole lot of sand. A better alternative is aspen, carefresh, shredded paper, eco-earth... Just avoid pine and cedar, and you should be fine.
I wish people wouldn't describe reptiles as "desert" animals, as nine times out of ten they're not from the expansive sea of sand, but rather these sort of areas. Arid is a much better subsitute. (Tiny Boidae for president 2016. Changing the reptile vocabulary one word at a time).
Also, knock the temps down a few degrees. The hottest spot in my animal's cage is 95°, and I feel uneasy going any higher. You can get a cheap thermostat to control this from LLLReptile, and I use zilla ones for all of my sand boas. They're on/off thermostats, so it might take a little fiddling to get it right.
Zilla 1000 Watt Temperature Controller
Hybrid Mode
