The only address that can actually use RBF is address A because it remains the original sender of the coins. B to C transaction is CPFP and yet to confirm so B also cannot use RBF.
This is wrong.
Assuming there's an RBF-enabled unconfirmed transaction from address A to address B and another RBF-enabled transaction sending the fund from address B to address C, both transactions can be replaced by a new one paying higher fee using RBF method.
If the transaction made from address A to B is replaced by a new one paying higher, it can get confirmed faster, but the transaction from address B to C will be invalidated.
If the transaction made from address B to C is replaced by a new one paying higher fee, both transactions will be confirmed faster.