She can just sign out of your account and into her own but it will do some taking to set things up again.
Create an Apple ID - https://support.apple.com/HT204316
Sign in with your Apple ID - https://support.apple.com/HT204053 - Mac and iOS
If another Apple ID is signed in you may need to enter the password for that ID to sign out of that ID first.
Set up iCloud on your iPhone, iPad, or iPod touch - https://support.apple.com/HT208681
She will lose her Apple Music since that is tied to an Apple ID.
You'll need to set up Family Sharing and family subscriptions if you want to continue to pay for her things.
What is Family Sharing? - https://support.apple.com/HT201060 - "Family Sharing lets you and up to five other family members [Apple IDs] share access"
Set up Family Sharing - https://support.apple.com/HT201088
Sharing purchased content with Family Sharing - http://support.apple.com/HT201085
I could probably provide you with a bunch of related links but that's a start. :-)