can paypal be used to purchase in-app purchases?

Hi, my mom was trying to purchase something for her game on my old iPad and she wanted to use paypal and i did not know that you could. once i found out how i added her paypal to the account and attempted to purchase it. well it took it out of my apple account and not her paypal. i have been reading and it says it can be used to purchase from the stores but does not mention about in-app purchases. i did comfirm that paypal was selected as the default payment method on both devices. Can someone please tell me if paypal can be used for in-app purchases?