A child holding a parent's key to their chastity belt does sound like alot of power, but if that's the agreement with the parent, let it be (2 consenting adults anyway). The best way I could think of to have control of the key is to have a glass/ceramic piggy bank with a lock on it, so it can be opened safely with the lock that only Katie knows the combination to. In emergencies, the piggy bank would be thrown to the ground and smashed opened, never to be used again, and that'll be proof enough if the key was taken by force. I don't know if this type of piggy bank exist, but that's the best solution I have.
Good luck to both of you and do your best to stay strong and keep wearing your belts. Keep checking for skin care and be sure to make adjustments, you'll definitely need it.
