What is Ophelia's reaction to Hamlet's letter?

In his amorous pursuit of Ophelia, Hamlet has written her a number of love letters. In one particularly gushing epistle, he even tries his hand at some love poetry, with pretty execrable results:

Doubt thou the stars are fire, Doubt that the sun doth move, Doubt truth to be a liar, But never doubt I love. (act 2, scene 2).

On the face of it, these letters seem to express genuine emotion. Ophelia certainly seems to think so. But as well as being the object of Hamlet's affection, she's also a dutiful daughter. She betrays Hamlet by passing on his love letters to her father, Polonius. The letters are a valuable commodity to Polonius, as they will be used by him to determine the source of Hamlet's "antic disposition." Moreover, Polonius is keen to break off any incipient relationship that might be developing between his daughter and Hamlet for reasons of social propriety. Ophelia, though the daughter of a senior court functionary, is socially inferior to a prince of the blood.
Polonius shows the letter to Claudius and Gertrude, who are also keen to discover the reasons behind Hamlet's strange behavior. Neither they nor Polonius have any realization of the moral implications involved in getting Ophelia to betray Hamlet in this way. They're not genuinely concerned for Hamlet's welfare—or Ophelia's come to that; all they care about are the dictates of high politics. Ophelia will continue to play the dutiful daughter and allow herself to become ever more deeply embroiled in her father's cunning intrigues. The end result will be death for them both; tragic, in the case of Ophelia; somewhat less so in the case of Polonius.