Marge Sherwood: Dick? Dickie? I know you can hear me. What am I doing, chasing you around...? I was going to say I would count to three and if you didn't open the door, but I won't count any more. On you. I won't count on you any more. Whatever it is, whatever you've done or haven't done, you've broken my heart. That's one thing I know you're guilty of, and I don't know why, I don't know why, I just don't know why.
Tom Ripley: I always thought it would be better to be a fake somebody than a real nobody.
Freddie Miles: Oh God! Don't you want to fuck every woman you see just once?
Dickie Greenleaf: Just once?
Freddie Miles: Absolutely, once. Ciao.
Dickie Greenleaf: Tom Ripley. Freddie Miles.
Freddie Miles: I mean, hey, if I'm late think what her husband's saying.
Dickie Greenleaf: You look gorgeous.
Freddie Miles: As always.
Peter: Officially, there are no Italian homosexuals. It makes Michelangelo and Leonardo very inconvenient.
Tom Ripley: Well, whatever you do, however terrible, however hurtful, it all makes sense, doesn't it? In your head. You never meet anybody that thinks they're a bad person.
Alvin MacCarron: I don't care for BS. I don't care to hear it, I don't care to speak it.
Answer: After running into Meredith, Tom's plan was to stay in the cabin with Peter the entire trip to avoid them seeing one another. But after Tom makes that suggestion, Peter tells Tom that he seen him kissing Meredith. He couldn't avoid or kill her since Peter already saw her. Family members also saw Tom with Meredith. If Meredith suddenly vanished or was killed I'm quite sure there'd be an investigation. Peter was the only option. No one is on board to report Peter missing. Once the boat docks, Tom will be long gone before they discover Peters body. Unlike Meredith, her family would be looking for her immediately since they're traveling together. I'm quite sure he'd much rather have killed Meredith, she meant nothing to him.