i am not sure if you can create a transaction with 1 satoshi fee using common bitcoin wallets. they usually force you to pay a higher fee.
unless you are talking about fee/Byte then it is a different story. 1 satoshi/Byte is a good amount most of the times and it will be confirmed soon enough. for example right now the mempool is empty and you may even see a confirmation in next block for such transactions.
so like this:
Wallet A sends btc to Wallet B with 1 sat fee.
Wallet B sends wallet to C before fully confirmed.
Once declined, money goes back to wallet A?
"money" never leaves your wallet until it is confirmed. think of it as checks that you write. imagine you have $1000 in your account and you write 2 checks each worth $1000 to two different person. until they go to the bank and cash it out you remain the owner of that $1000 and them with a promise of getting $1000.
writing difference checks is like creating different transactions. and cashing out that check is like getting the transaction confirmed. obviously one check (one tx) gives them money (can be mined). and the other is rejected.
that is why everyone waits at least for 1 confirmation or they do some kind of "risk analysis" if they want to accept 0 confirmation.
