turps

I'm sorry about your MIL.

Maybe you could get the thermostat sorted out while she's in hospital? Could you enlist the help of a doctor to tell them it's important for her to have heating to be able to go home sooner? When my MIL was still living alone we could usually get her to agree to do something by getting an authority figure like that involved.

It's so frustrating when people older people start to lose the ability to make good decisions for themselves. Sometimes you just need to grab the reins and go ahead with what needs to be done even over their protests.