She came to me last night to enter the password so she could play. After entering, I noticed that instead of temporarily disabling parental controls I was whitelisting the game. (She wasn't trying to trick me, just followed the prompts onscreen.)

I went into the app on my phone and un-whitelisted it and now she seems to be able to get into the game with controls enabled again.

This feels like a bug in how parental controls are implemented.