I also have a house with wet underfloor heating and rads upstairs. I’m not a professional but how about a radio controlled portable thermostat you can put in your daughters room, then individual thermostatic valves on all the radiators in the house? That should keep her room heated when the rest of the house is already warm, and the valves can all do their job individually. Probably work out cheaper than running a secondary heater in her room I would have thought too?
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