Need a refund

Follow the steps here: link-> Request a refund for apps or content that you bought from Apple - Apple Support

You can implement Ask To Buy on her devices to prevent that form happening. link-> Approve what kids buy with Ask to Buy - Apple Support

She can’t do that without your credentials. Lock it down. Apple has provided setting to allow you to easily do that.

Apple has been known to offer a one time refund in cases like this. Contact iTunes Store support.