How to split heating when partner uses 6x more than me?

Standing charges are about £1 a day, and I use maybe 80p a day of actual electric/gas. If she's away, the daily fee in total is around £1.80 a day. If my partner is at home, she uses about £5-6 a day with me turning the heating down because I can't breathe from the heat in the house. She wasn't wearing socks and complaining that her feet were freezing last night. Mentioned it to her, but her answer was "I want to live in a house where I don't need to have socks on because it's cold".

If her family come over, the living room is around 30c (not even an exaggeration, I've lived in Cyprus for 7 years) because radiators on max plus electric heater on max for the entirety of their stay. On top of this, there's an electric heater running in her room for about 10 hours a day or wherever her family are because the heating on max all day isn't enough for them.

I mentioned it to her that I am paying for half of the bills and it's getting silly, but she dismisses me. Am I in the wrong here? How would you explain to her that I can't carry on paying for her to walk around in summer clothing whilst the heating and electric heater is all on max all day long?