I can't decide between Edward or Rosalie.
I can't bring myself to put the blame on anyone else, since they really has very little insight into what they were doing, and what it could result in.
Edward and Rosalie were the only ones who actually knew they were going to upset some people.

I think everyone shares some of the blame, except possible Jasper.

Between Jacob and Bella (surprise, surprise the biggest morons in the series). Bella's reason for jumping off the cliff was idiotic. Jacob's reason for mentioning a funeral was stupid, too.

Between Bella and Edward. He shouldn't have run away, and she shouldn't have jumped off the cliff.

I don't see how anyone could connect jumping into the ocean to someone killing themselves. Really, does anyone think to themselves "what are the consequences to jumping into the ocean? Someone may see me, misinterpret my actions, then tell someone who may decide to kill himself in grief. I better not do it" I don't see that happening

What I do see happening is someone thinking "hmm, if I kill myself, people will be upset, I better not do it" or "if I tell him she's probably dead, he'll be upset and do something crazy, I better not do it" or even "if I'm bitter and cryptic and tell him her father is at a funeral, he may jump to the wrong conclusion, I better not do it" (but that ones a bit of a reach for me)

Blaming Bella would be like blaming me for someone's death for eating this chocolate pop tart because one time I broke out in hives after eating chocolate in front of someone, and that person may possibly see me eat this chocolate and assume that I'm allergic and call an ambulance as a preemptive precautionary concern for my health, and while the ambulance is on it's way, it strikes a pedestrian.
That would obviously be my fault, right?