81 is on her warm side, and currently I have a digital thermometer which is what every site seemed to recommend since they tend to be a bit more accurate.
Right now I'm using a heating pad on the under side of the tank, but it's not adjustable.
Is there possibly a better heating source opposed the the heating pads or possibly adjustable ones that anyone could recommend?

She's in a 20g tank with a rock type cave on the left side and a drinking/soaking dish more towards the right side but slightly in the center.
I'll be sure to take some pictures when I get my camera back from my dad to give you a better idea.

And, thanks for letting me know about leaving her alone for a week or so, I'll be sure to let her be for a bit to make sure she doesn't get stressed