The person asking for this advice mentions that we are discussing an elderly mother who has, for whatever reason, moved in.  Mom apparently has spent her lifetime using water in a manner not untypical for many Americans.

While many of us try to do more to conserve water than our parents might have, perhaps the best approach to all of this is to do whatever it takes to quietly, but not obviously, help Mom reduce her water use without her noticing the difference.  An aerator does tend to provide the perception of a stronger water flow while actually using less water, for instance.  Some...not all...reduced volume shower heads will do the same.

The main thing here is that Mom isn't going to be around for that many more years.  Should she be nagged about how much water she's using, or should the offsprung one shrug it off and enjoy Mom's presence for as long as she's still here?

I know which course I would take if faced with a similar challenge to my personal lifestyle.

Maybe Saturday night live should do a parady of "enviro dude", appalled that his roomy flushes after every tinkle, and uses too much toilet paper, and drives too far for a latte, and eats at Mcdonalds, and wears leather shoes, and buys environmentally incorrect toys for his baby nephew, and fails to recycle his post-it  notes. Environmentalism, when it becomes a religion, looks just as stupid.

Gawd.