Lol what a dumb policy, you should have asked her in her 10 years if it ever happened that an adult was using the children's restroom and the kid ended up not being able to hold it.
I would have done that, I had a crappy supervisor at the Target Food Court I worked a summer job at like 5 or so years ago. She was all bitchy one day and yelled at me "GRAB A CHEESE".... and I said "Cheese?" and she said "A CHEESE PIZZA, WHAT ELSE IS THERE WITH CHEESE ON IT!!!!!!", and I said "Nachos" lol.... and she got all pissed off at me, but she completely deserved it for treating her employees like shit.