Well pardon me, sorry for not knowing the specifics of the story based on your vague witterings.
Best sell the house then and look into renting a council property while applying for any benefits that might be available. Perhaps the world owes her a favour but there are people in these situations who don't have the benefit of property worth £1000's sat there. Nobody wants to lose a house but it's not a right to own one no matter how hard you've worked or how nice you are.
Your mum is able bodied, you say she's a qualified ITU nurse and she's doing favours for your sister. Well your sister needs to step up and take responsibility for her child so that your mum can try and get back to work then doesn't she?
And yes it would be nice to be able to spend time making sure the hospital are doing their job but sometimes you have to put your trust in these people so that you can eat and pay the bills.
Sorry for saying it how it is (in my mind at least) but this is life sadly, if he wasn't insured against such things then there isn't a huge amount you can do beyond asking for donations, benefits or going out to earn money yourself.
Sorry about that.