Shakespeare intended Ophelia to be portrayed as misdemeanor. Often changing sides she is never sure of what she is to do. The last moments of her life were simple she was picking flowers. In the movie she seems to look as if she wants to jump and the sense we get from the book shows the same thing she is tired of feeling unsure and looks for the simple way out of it. Gertrude did watch her struggle as her clothes weighed her down.
I believe the reason for her madness is the constant struggle with her father and Hamlet. She loves a man she is not allowed to love. The more she is told to stay away the closer she wants to be. Contributed to her demise would be how he father told her not to have sexually relations with Hamlet and she has already had them. She is struck with the unsure of both family and love. I do feel sorry for her, she is stuck in the middle and the longer she stays there the father away both sides pull leaving her all alone. If i was directing the play i would also represent her the same way. The playing with the bones in the "rubber" room or the looks her family gives off to her behavior. All these scenes tied together paint the bigger picture that with out Hamlet her life would of been different.