One thing we can see of Hero's thoughts from the text is that she thinks Claudio has gone mad, or insane. She thinks he is insane to be hurtling such wild accusations at her, as we see in her line, "Is my lord well that he doth speak so wide?" (IV.i.59). In this line, the word "well" can refer to mental health as well as physical health, showing us that Hero thinks Claudio has gone mad. Also, the word "wide" can be translated as "untruthfully" showing us that she is calling him crazy for making such wild, untrue accusations.
We also know that she is completely dismayed that she is being accused of lacking virtue. When Claudio asks Hero to "answer truly to her name" she asks how any one can disgrace her name by finding fault with her, pointing out that her name refers to a person of virtuous and "noble qualities" (IV.i.82-83, Random House Dictionary). Hero swears that she is still a virtuous maiden and is so shocked that she is being accused of such horrible things on her wedding day that she faints, which we see from Shakespeare's stage direction immediately after her father asks for a dagger to kill himself, as we see in the line, "Hath no man's dagger here a point for me?" (112). Hearing Claudio accuse her of these things feels like torture to her. We see her swear to the friar that she is still a maiden upon pain of being tortured to death if she is proved to be lying, as we see in the lines:
Prove you that any many with me conversed
At hours unmeet, or that I yesternight
Maintained the change of words with any creature,
Refuse me, hate me, torture me to death! (189-192)
Hero's fervency in proclaiming her innocence shows us just how bewildered she is by these accusations.