In Shakespeare’s Hamlet, what plot events undermine Queen Gertrude’s confidence?

Although Gertrude seems to be unaware of Claudius’s misdeeds at the beginning of the play, over the course of events, she starts doubting her assertions. Her beliefs are undermined when Hamlet murders Polonius and accuses his mother of betrayal. He reveals to her the truth about his father’s death and forces her to see her own villainy.

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