If I choose a light colour in WhatsApp on my phone it works - flashes, works fine. Do the same on hers and she gets no light whatsoever. I have set our phones up to have exactly the same settings, neither of us has any special apps installed (like Light flow) and pretty much all our system settings are exactly the same. Her LED toggle is switched on the same as mine and she is using the same SMS app. Neither of us has any rogue-looking apps installed. We both have the same SMS client and all apps are up-to-date.
Does anyone have a clue what could be going on here? Her light definitely isn't faulty as it works when someone calls - flashes green, lights red when charging and blue when she double-taps the screen to unlock.
I'm all out of ideas now. She is not wanting to do a full restore.