You gave a lot of detail here without giving details.
What is around 80? Is that belly heat or ambient air temp? I hope you have a TSTAT on the UTH.
If 80 degrees is belly heat what is the ambient temp? 80 is a little too cool for ambient air and 10 degrees too cool for belly heat. Get the ambient air up to 82-85 and the belly heat to 90-92.
Are you using the same enclosure she was in for 4 years? If not this could be one reason she is not wanting to eat. I recently helped rehome a 12 year old BP who was an avid eater. She very rarely refused a meal. The guy wanted to give her away due to going off for active military duty but did not want to give up the enclosure so he could get another snake when he returns in a few years. The snake was rehomed and never would eat. Tried assist feeding and it didn't work. Tried force feeding and it didn't work. She died after 8 months of stress and no food. This is the very reason I tell people to be prepared to care for the snake for up to 30 years.
One thing you may want to try is completely black out the glass tank and give her total privacy. Don't try to feed her every day. Try one day a week and keep it to that. A 3 month fast is not that bad for a 4 year old BP. Give us some more detail and let's see if we can help.