Intermittent no crank, no start problem?

“Little old lady car” intermittently won’t start.
The car has only 53,000 miles, most of them driven by a little old lady who drove only two miles to work each day. Battery is 2.5 years old, and voltmeter on battery shows 12.6 volts. Starter, starter relay and ignition relay are brand new. They were replaced in an attempt to solve the following problem.
The problem? My daughter, who lives two hours away from me, called me last week to say her car wouldn’t start. When she turns the key, the dash warning lights and air conditioning fan come on, but there is no sound from the starter or engine. The car had sat for two hours when this happened. After AAA towing was called, the tow truck driver had my daughter do one thing before he hooked up the Regal-- turn the ignition key. Surprise! The car started. She drove the car 10 miles to her home and parked it for 10 hours.

The next day, I drove two hours from my home to the car in an attempt to solve the problem. The car started fine, but I had parts to install. New starter, check. New ignition relay and starter relay, check. Battery tested at 12.6 volts. The car started up multiple times for me with no problem. I checked all the other relays, Maxi fuses, and mine fuses that had “ignition” on them, and they were fine. I plugged in an auto code reader into the dash before and after the starter replacement and no codes showed. After a one mile, 10-minute test drive around the college campus, I parked the car and thought I had solved the problem.
Unti 20 hours after I shut the car off, my daughter got in the car, turned the key, and no crank, no start. Dash lights and fan worked, but no sound from the starter. She waited five minutes and it started. It started four other times with no problems within a couple of hours after the first no crank, no start.
Any ideas what is wrong? The temperatures were lows in the mid-60s to highs in the upper 80s. The terrain is flat. Is it the battery? Car computer control? Alternator? Neutral safety switch? Something else?
The only time I had heard of this type of car problem was with mom’s Volvo, which left my mom stranded multiple times and had several mechanics scratching their heads. Ultimately, mom ditched the Volvo for a new Ford Edge.
Any ideas on what to check, change or replace on this “old-lady” car? Does it have a family “curse?”