My elderly mother is on my family plan and I am trying to restrict her ability to purchase subscriptions. (She does not realize when she is buying them.) How do I do this without pretending that she is a child?
You could try to use ScreenTime or parental controls.
See how to use Screen Time on an iPhone, iPad, or iPod touch by clicking here --> Use Screen Time on your iPhone, iPad, or iPod touch - Apple Support
Related information about how to use parental controls on your child's iPhone, iPad, and iPod touch to restrict access to features --> Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support
This is not all that great a way since if she knows her Apple ID and password she can remove the passcode. The only other way would be for you to reset her Apple ID password to something only you know.
Restrict purchases for adult on family plan
