Struggle!!

If she is under 18 she has been using it illegally (https://applecash.greendot.com/termsconditions/). You need to follow these instructions - To set up Apple Cash Family you must first close any accounts that children already had. Make sure that the balance is zero then go here - Manage your Apple Cash account - Apple Support next, go here - Set up and use Apple Cash Family. (Additional support links View and limit your child or teen's Apple Cash activity, Leave Apple Cash Family, Apple Cash and person to person payments limits)

turning it off does not close the account. if they went to that link Manage your Apple Cash account - Apple Support and closed the account, then sign out of your Apple ID and back in and try again.