I'm not sure about the background info like if this is her room just for now or for a number of years, or is this a house you'll be in for a number of years or if this is just a solution for this year alone.
If this is going to be her room for at least a few years and depending on your what winters are like where you are I'd probably look at a longterm solution, like a direct vent unit or something an HVAC company would install. It will cost more upfront but overall you'll probably save more in the long run, the safety features out weigh a standard space heater, and the room having a permanent unit would probably assist in resale if you ever do sell.
