How do I share Apple Music family subscription without giving free access to my cc in iTunes/App Store?

I signed up for the family plan for Apple Music and added my kids and my (adult) sister to Family Sharing, so everyone could listen to whatever they want. But, it turns out that my sister can now buy whatever she wants in the App Store or iTunes and I get billed for it.

Is there a way to only share the music subscription without sharing free access to my credit card? I do have my kids set up so they can make purchases with permission and, more importantly, they know I do keep track. But I do not want to pay for my adult sister's purchases and since she is an adult it's not like I can set up Ask to Buy - not that I'd want to keep track of her stuff.