This is an interesting solution. The problem is that your friend would need to trust you, as you would still have the private keys.
Not necessarily. DrBitcoin might have just started this thread in the name of his friend because he has an account on Bitcointalk. It doesn't have to mean he has access to the recovery phrase of his friend.
@DrBitcoin
Does your friend have reasons to believe that her original seed (the one in Ledger A) is compromised in any way? Has it ever been entered in a hot wallet, stored digitally, or shared over email, cloud, or similar online services? Has anyone seen it or had physical access to it that he/she was not supposed to have?
If none of that has happened, restoring your wallet via the recovery phrase solves that problem your friend has. She will have access to the same coins on Ledger B without making any transactions. After that she can reset Ledger A to factory settings and do whatever she wants with it. Any other solution will create an on-chain transaction.