it is clear that the scene on the boat is for Jaye and MC precisely to get over that episode (in which it is true that MC meddles in his sister's affairs without any tact, but Jaye reacts badly by spilling terrible nastiness at him and her father , with her justifications)
but that said, on the boat Christian is being punished for something NOT REALLY DONE 6 years earlier, for which 6 years earlier Jaye wanted to take care of it herself
add to that the fact that MC is still convinced that he is looking at the one who wanted to rape his sister, Jaye knows that's not really the case, but now as 6 years before she keeps it to herself
we are not talking about justice in any way, that was already done MC precisely 6 years earlier