Mum's bruised hands

This is how mum's hands looked after her recent hospitalisation. In fact, they've improved in this photo since she was first released from the ward. But they were so badly bruised because of the cannulas they put into her hands to accept the IV antibiotics and direct the flow into her body. A cannula is a small plastic pipe with a tube at one end and a clip at the other. The clip end faces out and the IV feed from the bag of antibiotics is fastened to it.

Because mum's skin is delicate and because she has the bad habit of taking the cannulas out of her hands when they're not connected to the IV feed, her hands become bruised like this because new sites for the cannulas have to always be found. It'll be the same story if she's readmitted to the hospital again at some point in the future. But when she got out of the hospital she forgot that she had been in hospital, and so she had to invent a reason why her hands were so badly bruised. This is how she works it out:

I don't know what's wrong with my hands. Something to do with an unrestrained horse in the back of a car with no bridle. I don't know how I got into that situation but I was in a sedan with a horse in it.

I tried to talk her around it:

It's not true you know.
Why?
You were never in a car with a horse in it.
Oh [well], it was a good story.

Finally she accepted my version but you can be sure that if I bring up the subject again tomorrow when I visit her in the nursing home she will revert to the story of the horse in the car. That's just the way dementia works. It seems strange to us, almost willfully blind, but to her it's the only realistic solution to an intractable problem: how did her hands get so banged up?