This is probably a learning experience to not let your 5 year old sister to use devices signed into your account. Accounts should be shared the way you would a toothbrush.
You can ask for a refund but you may not get all of them. Apple has to take things on trust because they cannot reach out and remove something once purchased. At some point they may figure that one or two are okay, but more?
Here's how to request an app or media refund from Apple (From: Request a refund for apps or content that you bought from Apple - Apple Support - see the article for more detail.) If you bought this in the EU from a third party, see: About purchases not billed through the App Store or the App Store's In-App Purchase system - Apple Support instead.
1. Sign in to https://reportaproblem.apple.com
2. Tap or click "I'd like to," then choose "Request a refund."
3. Choose the reason why you want a refund, then choose Next.
4. Choose the app, subscription, or other item, then choose Submit.
If you were charged for a subscription that you no longer want, you can also cancel the subscription using the directions in this article --> If you want to cancel a subscription from Apple - Apple Support
Read this support article for information about how long it takes to receive a refund (if you are granted one), and how to check the status of a refund for apps or content that you bought from Apple --> Check the status of a refund for apps or content that you bought from Apple - Apple Support
Note that if you allow another person access to purchasing on a device you are taking responsibility for things they do while using it. Apple offers these proactive features:
You can use Screen Time to prevent unintentional or unauthorized purchases from the App Store and other Apple services. —> Use Screen Time to turn off in-app purchases on your iPhone or iPad - Apple Support
Require a password for App Store and iTunes purchases
Require a password for App Store and iTunes purchases - Apple Support