Ophelia is in love with Hamlet, but like so many women, she is at the beck and call of her family first and foremost. Ophelia is not unintelligent, she is simply weak-willed. She doesn't know what she wants, so she lets other people decide for her, namely her father and brother. Hamlet's love letters are at odds with her father's wishes, and, because she is not able to form individual thoughts and opinions, she becomes confused as to what she really wants. Ophelia's weakness of mind and will, which catalyzes her obedience to her father and thus destroys her hope for Hamlet's love, finally results in her insanity and eventual death.
When her father had challenged the honor of Hamlet's intentions, Ophelia could only reply "I do not know, my lord, what I should think" (III, iii). Used to relying upon her father's direction and brought up to be obedient, she can only accept her father's belief, seconded by that of her brother, that Hamlet's "holy vows" of love were simply designed for her seduction. She was to obey her father's orders not to permit Hamlet to see her again. Her father also wanted to prove Hamlet's madness to the king. He used Ophelia as bait so he and the king could listen to Hamlet's words. Ophelia willingly obliged to her father's desires. By not thinking for herself and only doing as her father wished, she ruined her chances of love with Hamlet.
Hamlet put pressure on Ophelia by expecting her to surpass his mother's shortcomings and be an epitome of womankind. He searched her innocent face for some sign of loving truth that might restore his faith in her. He took her mute terror for a sign of her guilt and found her to be a false person, like his mother. In his letter to her, he addressed the letter to "the most beautified Ophelia" and he terminated the letter with "I love thee best, O most best, believe it" (II, ii). He used the word "beautified" to display a sincere tribute, and it is apparent he still loves her. His attempts to win her affection are not triumphant. Ophelia is still too much under the influence of her father to question his wisdom or authority, and she has no mind of her own to understand how much she has made her lover suffer.