one good way to keep them warm is to make sure there is no breeze in the room at all. try buying one of those cat beds that have like a roof over them...
http://www.petco.com/product/104515/...tty-Cabin.aspx
something like that with a small baby blanket and a rice microwave heat pad under the bed itself would probably keep yur kid as warm as needed.
This however being the cheap and easy solution, a heated pet bed would work as well. maybe keep her in a pen and on the outside of the pen face a space heater towards her in a serperate room.