I did warm the mouse up. I thaw the hopper in one of those small plastic baggies, then I put the baggie in an old pill bottle filled with hot water (but not like boiling). I leave for about a half hour. I check to see if it's all warm and thawed before I offer though, and if not I hit it with a hairdryer.
Maybe she is going into shed. I saw her when I checked the temps, and I might have been imagining it but it looked like her cheeks were a bit pink? I'm not sure if that means anything.