Has your Mum ever heard of a condenser dryer? These can be put in any room with enough space. Just don't put them on a carpet so they get enough air flow. I would never have managed without mine, which stood in my bedroom while husband lived with me before going into care.Going back just over ten years ago now, when my late stepfather needed to go to the toilet a couple of times in the night - no dementia involved but he had two fractured hips so had severe difficulty walking - my Mum just couldn't cope with the extra bedding changes and washing involved - that she insisted on having two separate single beds instead of the double bed. Ray objected vigorously (he thought it was his moral right as a husband to share a bed with my Mum, his wife) but he was in no position to do anything about it.
Although Mum did continue to suffer from lack of sleep until Ray went into residential care, at least with the two single beds when she had to change Ray's sodden bedding in the middle of the night it helped reduce the amount of washing she had to cope with. Drying the bedding was always the problem because Mum's kitchen doesn't have room for a tumble dryer.
Perhaps if you have room for two single beds instead of a double, this option might help by reducing the amount of washing you have to cope with?
Condenser dryers have a water drawer, which pulls out for emptying. There is no plumbing work to be done.