Disabling Family Sharing for a 14-year-old on iPhone

I would like to stop the familiy sharing. She cannot set-up anything without me, the possibility to stop family sharing is disabled on both phones. She cannot set-up her bank account number on her phone

[Re-Titled by Moderator]

Original Title: Hi, I set up myself es a guardian for my (now) 14 years old daughter and I want to disable it, but my phone tells me until she is 13, her phone tells until she is 16 I cannot do it.