Thanks for the response and info. I got involved in water testing and treatment for a while in a minor way and it is just an interest. Not much science behind the interest, though. I got involved with wells across the Eastern Missouri/ Western Illinois area and then when I retired I wound up doing water testing/monitoring along the Missouri/ Arkansas border.
One of the things that has always impressed me was how much well water can vary over a very short distance. The fact the we can still get good water also impresses me.
I lived less than ten miles from a super-fund cleanup site where the underground water will peel the paint off your car but our well, which was monitored monthly by EPA standards, never showed anything. Something we were always told on every inspection was that our pipe which led down into the well should have been 12" rather than the existing 8" to prevent ground water from running into the well.
Unfortunately, there are millions of wells that are poorly built or abandoned and uncapped ,where surface water can run in and pollute the water in even the best wells. Just something to be aware of for any future questions but this could be one reason for the water to vary.
I won't bet on testing or your mother when it comes to knowing hard water! Testing is good for for overall knowing what's happening, mothers are tough to beat.