Family member being asked to pay again for app I already purchased and shared with her?
If Family Sharing is enabled, they should be able to re-download paid apps at no additional cost by tapping App Store > Purchased. 

If they are on separate Apple ID's linked through Family Sharing they need to choose your account from the top right corner of the Purchased section in App Store. Then they should be able to download the paid app(s) at no additional cost.