She drowns herself out of madness. But I think her madness has a point to it. Tis told me, he hath very oft of late Given private time to you, and you yourself Have of your audience been most free and bounteous. In honorable fashion. Nymph, in thy orisons be all my sins remembered.
Orisons are prayers.
The implication is that they have sinned together. He knows she is deceitful from having just heard her agree to spy on him. The best way for him to know she is dishonored is if he has dishonored her. Lord, we know what we are, but known not what we may be. After all, she is no longer the daughter of the King's chamberlain.