Poor girl....you might try lowering the basking temp. to 100, that might help a little with her frantic attempts to get out of the tank. Of course that's not the main concern here, i understand, so about the lay box. They don't need it to be warm, just room temp. in the upper 70's is fine. There should be a good amount of sand, about 10" deep and you can pile it up on one end to be even deeper and then start a tunnel with your hand.
As for her teeth, some adults will develop brown stains as they age....it's not necessarily a health problem. I will make a suggestion to get a baby toothbrush , wet it and just gently + quickly give a swipe here + there as you get the chance. Be sure to keep a TIGHT grip on it for the obvious reason.....you don't want her to try + swallow it, although I doubt she'd try. It might help to get a bit of stain off, but I wouldn't worry too much about it. If you don't feel comfortable doing it, then don't bother trying.