If that description is correct, your sister messed up because she completely missed the step where she converts a private key into a public key, and uses the public key to feed into SHA256, then RIPEMD160, then Base58.
Missing that step created an invalid address that is completely unrecoverable.
See? This is
exactly why people should be using wallet generators like ZPyWallet to make their keys, instead of trying to do it by hand.