Lot of questions lots of answers within many threads posted here I can touch on a few in no particular order..

First I recommend getting a food scale and see how much she weighs I got mine from Amazon for $18.
Next feed her according to that you can Google it on feeding size charts for ball pythons or something like that. I tend to feed my snakes on the smaller size I have a female that is 1, 300 grams and another that is 1100 and one that is 700gr. They eat a small rat once every 4-5 days.

Your temp is too low..
Hot side on mine are 89-92 with a ambient temperature 78-82. I keep mine in a rack unit.

Water bowl on cool side or towards middle.

40 gallon is on the large size I'd recommend a hide box on both hot an cool side some Small so she can squeeze into not overall large when she starts to wear it as a hat then get a bigger one...
Cover the top of tank at least 90% or greater use plex glass or aluminum tape which would hold heat an humidy better look on Amazon for a hydrometer there anywhere from 6 to 20 bucks don't buy the ones they sell at Petco or PetSmart do you have a heat gun again do not buy the analog versions at Petco or PetSmart they're garbage gonna run you about 20 to 50 bucks.

Are you running thermostat with a probe you can pick up one I use vivarium v200 they are about $120.
Put probe between heat pad an tank I assume your heat pad is a undertank so the probe will be sandwich between the two.

Live to frozen transition can be as simple as just taking the rat and dangling in front of her with tongs and see if she takes it or putting the rat next to her hide box and leaving the room nice and quiet and dark as possible I don't feed my life the quicker you can get her on Frozen thawed the better


Sent from my Pixel XL using Tapatalk