Hi Monsoon,
my Granny's 97 and I know where you're coming from. I sleep over there on Sunday nights for the last few years (we all do) so we get to experience what she does. Luckily, house is snug with a lot of improved insulation & windows courtesy of the council (she owns her own house) and a well tended open fire. Many of us are not happy with an open fire arrangement because of the risk but its something she enjoys to look at. She was born in 1913 after all, so an open fire means the world to her.
But...... having said that, if you look at this link here on Boards.ie, I have to say I'm finding a digitally controlled kerosene heater intriguing. Costs about 270-290 but pushes out excellent heat. See
http://www.boards.ie/vbulletin/showthread.php?t=2056086261 Also has a carbon monoxide detector. Which is vital !
You could also opt for the older technology wick style. They are not digitally controlled and a bit more fussy to start / stop etc and for that reason may not be suitable around a very elderly lady, where people mightn't drop in for 5 hours or more at a time. So, as others say, either ceramic / halogen heaters or this kind of high tech paraffin / kerosene heater.
Hope that helps and, as you know, the biggest killer of all is winter. always has been, always will be. Best wishes this winter and mind yourself too.