I think Ophelia seemed vulnerable. She was easily talked into doing things. This is probably because she was so close to Polonius. She let her father set up Hamlet and went along with it. She lacks strength to stand up for her beliefs in a way.
The major factor that contributed to Ophelia death was Hamlet's change in behavior and attidtude. In my opinion along with this pressure and then later on her father dieing really caused her to go off her rocker. She kind of goes crazy after all these tragic events occur in a row and is emotionally unstable. However I don't think that she intentionally killed herself at all. The branch snapped as an accident. I believe Gertrude, Hamlets mother, witnessed her drown. How else would she have known what had happened in such intricit detail?
