Hi ashsym
welcome to the Apple (user-to-user) Community.
Re: "Enabling mail account : I disabled mail on my daughters iPhone",
Apple Support's article:
Use parental controls on your child's iPhone, iPad and iPod touch – Apple Support
says
Eg: Allow built-in apps and features
You can restrict the use of built-in apps or features. If you turn off an app or feature, the app or feature won't be deleted, it will just be temporarily hidden from your Home Screen. For example, if you turn off Mail, the Mail app won't appear on your Home Screen until you turn it back on.
To change your Allowed Apps:
- Go to Settings and tap Screen Time.
- Tap Content & Privacy Restrictions.
- Enter your Screen Time passcode.
- Tap Allowed Apps.
- Select the apps that you want to allow.
If needed:
What to do: If you forgot your Screen Time passcode - Apple Support
Scroll to:
"How to reset the Screen Time passcode for your child's device" in above article.
All the best :-)