Ophelia is a representation of an oppressed women in the Elizabethan era. During this time hysteria and madness was attributed to women only and hence her death wasn't a surprise. She can be seen as a tragic character who was weak and driven to her death by her male counterparts or she could be seen as headstrong and taking control of her own life in the only way she could.
If her death was an accident, she would have drowned because she did not have the will to save herself, reinforcing the belief that women were weak-willed and foolish. However if she purposefully killed herself she could be seen as independent and someone who subverted the social expectations of a women during that time. She turned her oppression and yielded the only power she had over her life. She also did this without much hesitation, which, in comparison to Hamlet's lengthy indecision to kill himself, could be seen as headstrong and purposeful