My daughter has changed her passcode
I’m supposed to be in control of her phone she is 11. And she changed it and I need to change it back
Question marked as
Well, only SHE can change it now.
Time to exercise your parental prerogatives and authority.
Going forward, you can restrict her by using parental controls as outlined here:
Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support
(Specifically in “Other Settings and Features)
You might ALSO consider restricting changes to her AppleID as well.
Note that YOU need to configure the screentime on HER phone selecting the “This is a Childs Phone” option.
The screentime passcode used needs to be known ONLY to you AND she must NOT know your AppleID password or device passcode.