I know this doesn't really help but if her housemates are at least being reasonable - keeping it on low, wearing jumpers and socks and not expecting to live in a tropical paradise then I think I'd just go with it. It's not worth damaging the relationships and having falling outs especially as she could end up living with much worse.
At uni I lived in a big house with 7 people. We were all keen on saving money and had the heating on a timer and everyone wore warm jumpers etc in winter.
We had one housemate who was the only one who never went home for the holidays. Once we left she used to take it off the timer, turn the thermostat up to 24 degrees(!) and walks round literally in t-shirts and shorts. In December.
She left it on 24 hours a day and even left it on while she went staying at her boyfriends house for 2 days and the house was empty. We found out when someone popped back to grab something and came into a very warm and empty house.
At one point the landlord came over and messaged us asking if there was an issue with the heating and if we knew the house was so warm.
The housemate refused to accept this was an issue and then the massive bills came she insisted we were all responsible for splitting it evenly. We had to pay but she left soon after as it caused massive arguments in the house.
There are so many stories of crazy housemate experiences and it could be much worse. Uni is a strange experience. You take all these teenagers who've never been away from home before. They're technically adults but they've no life experience. You put them all in a house together. They've all not much money and everyone thinks the way things were done in their house growing up is normal.It's a strange time and there's bound to be conflicts but I think it's good to choose battles where possible.