BruceAndNosh
stuff that was accurate and true but she'd left out a vital piece of info so it all sounded bonkers. She would jump from subject to subject with no logic but I knew from experience that there was a valid connection that she left out
This sounds like a fairly standard three-sided conversation if my mother and two of my aunts got together and held a gabfest. They all talked at once and they all leaped from point to point like mountain goats from rock to rock, but it became apparent afterwards that first, each could tell you what the other two had been talking about, and second, even if things seemed disconnected there was always a valid link.
I do it too. I once had a tape recorder on by accident when I was talking with one of my friends, and about a year later we came across that recording and played it back; without the facial expressions and the hand gestures it was very difficult to decipher what had been going on, because we both had grasshopper minds (and both missed out the essential words "that reminds me") and did a lot of referencing to previous conversations and to texts from school, the words of popsongs, and stuff from TV.
Maybe your mother just assumed that people who knew her well would know what she meant. As did my sainted mama , sharp as a pin to the day of her death apart from suddenly losing nouns, all her life, which led to the immortal phrase, "Pass me the thingummy, could you? Off the wotsit. Oh, you know, over there with the other ones." (So I passed her the right-sized wooden spoon out of the jug on the dresser...)