I'll second the suggestion of getting her a mattress pad. I've been using one for years. We have a wood stove in the living room that heats the living room and kitchen, but the rest of the house is pretty much closed off for the winter. There's about a foot high space between the hallway and unused bedroom door where air from the heated section of the house gets into the bedroom. I haven't been cold yet. It was -18F the night before last. The one I have has three different areas for temperature settings, so I can have the foot part of the bed pretty warm, the middle lukewarm and the top just enough to get rid of the chill of the sheets.