Remove child from family sharing

All purchases made by an Apple ID are forever tied to it. So anything that was purchased by that account, will be unavailable once the account is removed or deleted.

Unless there's an exceptionally good reason to change an Apple ID, it should not be done. Your daughter should have continued to use that account, and update it as necessary if required. There is almost never a reason to stop using an Apple ID.

If the account is now over 13 years of age, it can be removed from the Family Group. Otherwise, you'll need to request that Apple delete it entirely, which will delete all purchases made by it and all content stored in iCloud by it will also be wiped out.

See the "Remove someone from your family sharing group" section here: Leave Family Sharing - Apple Support

Child accounts can only exist as part of a Family Share. You can either transfer the account to a new Family Share, or get the account (and therefore all of its purchases etc.) permanently deleted : How to delete your Apple ID account - Apple Support

Family Sharing -  Transfer a child to a different family group - Apple Support?

If necessary, contact Apple ID Support.

Apple ID Support

Apple ID Support (2) 

Apple Support by e-mail or chat    Work through the screens to get a chat option.  You may need to pick a problem that is slightly different than yours to get a chat option.  

Apple Support using Twitter

Or fill out and submit this form.          The form is for iTunes, but it will get passed to the ID Support section.