apple id

Create an Apple ID for her.

Apple ID - create a new.      

Apple ID – Create         

Family Sharing.         

Family Sharing - Set up.        

When changing to the new ID, there may be some data loss, but you can minimize it. If syncing photos with iCloud, ensure Optimization is turned off in Settings/Your Name/iCloud/Photos and/or in Photos/Preferences/iCloud. Then make sure full resolution photos are on the device/computer. When signing out of iCloud, if asked whether you want to retain data, choose yes. Messages conversations will be lost if they are addressed to the ID. See the article below for other places that the old ID should be removed. See Winston Churchill's response in the below discussion. Also set up Family Sharing to keep access to your apps/purchases. 

How to switch Apple IDs on your iPhone or iPad.      

How to transfer all files from one iCloud account to another.        

What to do after you change your Apple ID or password - Apple Support.     

Could you put a few more words around your particular situation, and some background on your goals?

An Apple ID is your account. it can be associated with an Apple email address, or email addresses from other services.

I’m here glossing over older Apple IDs which were not required to be an email address. And I’m glossing over setting up alias email addresses, which is an option for Apple email addresses, as well as some other email providers.

You can use multiple Apple IDs on an account if you are talking about a Mac user account? To be clear, each Apple ID yields an Apple ID account.

You are very welcome. Stay safe.

You are welcome.