No, you are wrong and so is everyone else "you are talking to". The thing all of you are missing is that censoring Alice is a race, where the attackers (secret miners) have to get a longer chain in the time it takes the public miners get only two blocks. Remember bittrex gets its blocks only from the public miners.

I already did the analysis, so I won't do them again. But the chief considerations are: (1) attackers have to mine secretly until they have a longer chain, (2) each N-length race is probabilistic, and (3) exchanges and vendors will confirm the transaction after two public blocks.