I'm strangely pleased that you shared this Alison.
It's not really something any otherwise tough and canny person (like your mother too) would talk about..
I know I don't acknowledge it much myself.
Our house is 400 years old and backs on to a graveyard. I've always been 'sensitive', apparently as a small child would regularly ask about or talk to people who 'weren't there'.
I often turn around in my kitchen and flinch as though I'm an inch from bouncing off somebody.
When sitting on my sofa I sometimes feel someone standing behind me. They occasionally rest a hand on my shoulder.
My 20yr old son has inhereted this, for sure. When he was very young (4/5ish), looking out of an upstairs window he told me, conversstionally, there was a lot of people by the graves that day. I saw nobody. He said it was one person standing next to the stones of quite a few graves.