Hi milesbeecham,
Thank you for participating in the Apple Support Communities. We understand your daughter will be switching from a family plan to an individual Apple Music plan and she doesn't want to lose her data or playlists. Her data is associated with her Apple ID so she shouldn't lose any data. However, we recommend not having any lapse in her subscription. If she were to be unsubscribed for a period of time, she would lose her data. This article explains how to switch: How to switch to a different subscription plan.
"Switch your subscription plan on your iPhone or iPad
- Open the Settings app.
- Tap your name and then tap Subscriptions.
- Tap the name of the subscription that you want to change.
- Tap See All Plans, then follow the onscreen instructions to complete your purchase.
- If you've chosen a subscription that you can share with your family, turn on Share with Family. (Can't see Share with Family? Set up Family Sharing or join a family, then return to your list of subscriptions and turn on Share with Family.) If you don't want to share the subscription with your family, turn off Share with Family.
Switch your subscription plan on your Mac
- Open the App Store app.
- Click the sign-in button
or your name at the bottom of the sidebar. - Click Account Settings at the top of the window. You may be asked to sign in.
- On the page that appears, scroll to Subscriptions and then click Manage.
- Click Edit next to the subscription you want to change.
- Choose a different subscription option.
- If you've chosen a subscription that you can share with your family, select Share New Subscriptions. (Can't see Share New Subscriptions? Set up Family Sharing or join a family, then return to this page and turn on Share New Subscriptions.) If you don't want to share the subscription with your family, turn off Share New Subscriptions.
Switch your subscription plan on a Windows PC
- On your PC, open iTunes.
- From the menu bar at the top of the iTunes window, choose Account, then choose View My Account.
- Scroll to the Settings section. Next to Subscriptions, click Manage.
- Click Edit next to the subscription you want to change.
- Choose a different subscription option.
Switch your subscription plan on your Apple TV
- Open Settings.
- Select Users & Accounts, then select your account.
- Select Subscriptions.
- Choose the subscription you want to change.
- Choose a different subscription option.
- If you choose a subscription that you can share with family members, make sure you have set up Family Sharing or joined an existing family group."
We hope this helps.
Take care.