Do you have a desk lamp or something small that you can put directly over the enclosure? Do you have handwarmers that you could wrap in a towel and put in the enclosure? You could try moving her to a smaller in enclosure that is easier to heat just temporarily. Hot water bottle might work for a while.
If you have a cooler and 2 one gallon water jugs, then put the jugs into the cooler after filling with hot water. Put a board on top of the jugs then add tortoise with a blanket. Check temperature and leave top of cooler open just a small crack.
Otherwise, put the tortoise in a box and put the box in the bed with you. Box needs to be uncrushable.
Oh no, I understand this---but how cold is the home? If the home is in the high 60 to 70s then the tort should be aok through one night....I however would not let the tort remain within the enclosure if the party keeps the humidity high....
Wait. What did you use to keep the tortoise warm at night before the light went out? Were you leaving the light on 24/7? Yikes! Poor tortoise had no night time? You need a day light and a night heat source. Get yourself another ceramic fixture and plug in a ceramic heat emitter on a rheostat for night time.
This is a good thread. It helps every new tortoise keeper to realize they need to have alternate plans in mind for emergencies. How warm is it on top of your water heater?
Not related exactly, but if life or death you can always put in a small container, and inside a larger sweatshirt that you're wearing. I used to transport my lizards in bags underneath my shirt for long drives to and from college. It was a little overkill, but made me feel better.