How can I have 1 family member in family sharing use a different credit card for purchases?

How can I have 1 family member in family sharing use a different credit card for purchases?

I have a kid in my family sharing that I would like to have use her own credit card to track her spending and responsibility. It should be under her apple ID, which she has her card information in her profile, but anytime she makes a purchase or subscription it bills to my credit card.