with a child account, how do I remove her access to all of my data, contacts, and phone?

RusticMum wrote:

Thanks MrHoffman - but since she is under 13 I have to create an Apple ID for her and because of that her new iPhone isn't receiving or sending through her own phone number but rather using all of my information instead. Any way to change that?

An Apple ID is per-person.

You’re not sharing an Apple ID.

You’re getting everybody’s data tangled.

Again, what you are encountering is expected and normal behavior for one person; unshared.

It’s undesirable behaviour for multiple people; for sharing; tangled.

What to do?

Stop sharing.

Set up a Family Sharing group from your Apple ID..

Set up Family Sharing - Apple Support

Create a new Apple ID for the scion, transition the iPhone to the new owner, and sign in under the newly-created Apple ID, and join the family group.

How to create a new Apple ID - Apple Support

What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

RusticMum wrote:

with a child account, how do I remove her access to all of my data, contacts, and phone?

There is no such access, unless the Apple ID is being shared, or the iPhone or iPad was switched while not reset when still populated with your data.

Not sure what you are asking, but this info might help:

Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support