Buy a new one. Look for a UL or CSA mark, and it should be okay.
If it doesn’t have one, avoid it.
Also, give the general construction a good visual, because sadly there are goods being sold in the US and Canada with illegitimate UL and CSA tags and holographic labels. The CPSC and UL try to stay on top of the problem, but they’re still chasing ever inventive importers who devise new ways to fool the buying public.
A search of the UL website seeking reports of counterfeit UL marks returns 22 hits.
I have one concern about the mattress pad. She is almost three and just starting potty-training. Which means the dangerous bed-wetting time is coming.
Do they have protective covers?
Probably not. The one I used never really got that hot.
I have no idea, but I’m pretty sure that the wires are insulated pretty well. Mine was a polyester pad with the wires running through it. I was a little girl when I got mine, so I’m sure I spilled juice and such on it over the years.
Some more thoughts on this if you will. Aside from the cold room, there seems to be the other issue that your daughter is, for one reason or another kicking off the blankets. I think it would do her good to look into why.
If it is because she is getting too hot under them, she then will remove them (knowingly or not), then get cold. Heating up the room might cause her to kick them off sooner (or even more so if the blanket is electric).
If heating up the room doesn’t seem to help the blanket kicking, some suggestions you didn’t ask for is to try a lighter blanket, feel her extremities right before she kickes them off (or right after - but not so long as she would have reajusted to the cold temps), or leave her feet not tucked in.