I have an issue with heat, too. I'm just plain miserable when I'm cold!
Get an electric blanket (or electric throw) and use it as a mattress pad. Set it on low. In other words, sleep on top of it and make sure you have a nice down comforter. This will keep all the warmth in, at least, while you sleep. Using flannel sheets will also add to the warmth factor.
See about getting a new furnace. If your credit is good you can get a 0%/12 months no payments, no interest deal @ Home Depot or Lowe's. If your mom is a senior I believe there are tax credits and such for these kind of upgrades. You just have to put the time into some research on this. It will make for increased home value and a happier you.
