Check your purchase history. If she is doing the purchasing you will have to ask her to identify the purchase. Apple also sends you a receipt for any charges made so have a look at those.
The support article If you see 'apple.com/bill' on your billing statement - Apple Support and the related article Get help with charges from apple.com/bill - Apple Support explain how you can check your iTunes and App Stores purchase history, cancel subscriptions (remember that these need to be canceled at least 24 hours in advance), and track possible sources of unrecognized Apple charges you may see on a bill. These may be purchases by Family Sharing members, others sharing your card (such as a spouse or partner, or a second Apple Account you have; you may not see a receipt).
The article also provides a specific link for contacting Apple if you cannot trace the source of charges, e.g., if you subscribed to something directly with a third party, see: About purchases not billed through the App Store or Apple In-App Purchase - Apple Support instead. In that case you need to work directly with the vendor, not Apple. See also: Fabulous SAS - Unethical app, please dele… - Apple Community
If you use Apple Card you may find this document helpful too ➞ If you see an Apple Services charge you don't recognize on your Apple Card - Apple Support
Also note this service: View your App Store and iTunes Store purchases directly from your financial institution - Apple Support
which may let you view Apple receipt details when you are signed into your financial institution website or mobile app .
If using Family Sharing and viewing purchase history under Report A Problem, make sure the “Apple Account” box is set to “All.” If a purchase is listed in your purchase history and you want to ask for a refund, read this article about how to request a refund for apps or content that you bought from Apple ➞ Request a refund for apps or content that you bought from Apple - Apple Support Remember that many apps have trial periods with subscriptions that then start automatically unless you cancel them in time. If a Family Sharing member made the purchase then you need to discuss this with that person. They would have to initiate any refund request.
And from this support article --> How apps, content, and subscriptions from Apple are billed - Apple Support
"Which payment method is charged?
When you buy items or pay for subscriptions, Apple automatically attempts to charge your payment methods in this order:
1. Apple attempts to use your Apple Account balance to cover the full amount. This is at the top of the list always, but isn’t what is referred to as the “primary” payment method.
2. If you don't have Apple Account balance, you don't have enough to cover the full amount (balance will be used first, up to whatever it can cover), or an item cannot be paid for with Apple Account balance, Apple instead attempts to charge your primary payment method (typically a credit or debit card, but varies according to country). The primary payment method is at the top of the non-balance list in Settings on your iPhone. You can control which payment method is at the top of the list. [See: Add a payment method to your Apple Account - Apple Support ]
Don't confuse having to have a payment method present as an indicator it will be used. Apple may require a payment method be present even if it doesn't use it.
3. If there's a problem with the primary payment method, or if the primary payment method can't be charged for the full remaining amount, Apple attempts to charge your other payment methods in order from top to bottom. If none of them can be charged, Apple may try again." See also sections B and H of Legal - Apple Media Services - Apple
Some purchases aren’t charged to your Apple Account balance
● You can't use your Apple Account balance to send gifts or gift cards.
● For some recurring charges, like AppleCare+, you can't start your subscription with Apple Account balance. But as long as you keep another valid payment method on file and your Apple Account balance would cover an entire charge, your recurring charge will pull from your Apple Account balance (see the article for more information).
● Some subscriptions might not be charged to your Apple Account balance.
● If you use Family Sharing, your family members can't spend your Apple Account balance. Funds that you add to your Apple Account balance are available only to you.
