How do I lock my child's iPhone for a week when they keep unlocking it with the password?

Change the passcode.

Take the phone away for a week.

Reminder her that there are consequences for one’s actions.

Technology can be an aid to parenting, but not a replacement for it.

Hello~ Any help here?

Use parental controls on your child's iPhone or iPad - Apple Support

Or as *Lawrence Finch* suggests…

Set a passcode on iPhone - Apple Support

If nothing there helps …simply take the iPhone. That should do it.

~Katana-San~