Never been randomly selected (PreCheck or otherwise) for further screening in the last several years. In my experience, at least, the odds seem way less than 50/50 to get the full monty when qualifying for PreCheck, or at all, for that matter. Maybe she just got REALLY lucky...

Right after 9/11, I did get "randomly" selected practically every time I flew. My record is 4 "random" selections in one trip involving 2 non-stop flights. I was "randomly" selected at the checkpoint AND the gate on both the outbound and return flights. I was dating my now-wife long distance at the time, and she laughed when she would drop me off at the airport because I would get selected at the checkpoint almost every time.