Family account - accidentally redeemed gift card on wrong, non-organizer family member account

On a family account, I accidentally redeemed a gift card on the wrong family member's account - not on the organizer's account. A rep told me gift cards cannot be transferred between accounts.

We want to use the gc for several monthly subscriptions (including iTunes music). Absent asking for funds which are unused to be refunded to the original gc, wondering ...

• How can we somehow use the gc for all our subscriptions?
• Can the organizer somehow change just her iTunes Store account to the non-organizer's which has the gc funds?
• If yes, will this affect our existing music and accounts?

Any advice/info is appreciated!