This is the enclosure (she is active again and pictured for scale): the left side is the warm side (with the hide over the warmest area of the UTH) and the right side is the cool side.

The main process is warming the mouse in a bag in a bowl warm/almost boiling water for 10 minutes or so to thaw out, and once it is relatively warm I have tried offering as is and warming with a hair dryer on low to get her interested. I then take the mouse by the tail with metal tweezers/tongs and dangle it relatively in front of her face, and then shake it/bounce it to make it seem alive.