Macbeth considers his wife to be his
dearest partner of greatness
as he writes in his letter to her at the beginning of Act I scene v. She does most of the planning of the murder of Duncan. She tells him to show courage, and their plan will succeed
But screw your courage to the sticking-place,
And we'll not fail.
Her advice in Act II scene ii, after Macbeth is disturbed that he cannot say 'amen' now he has killed the king is prophetic as it signals her own demise -
These deeds must not be thought
After these ways; so, it will make us mad.
When she advises him to clear up after the murder, it is an image which pervades her later sleepwaking-
You do unbend your noble strength, to think
So brainsickly of things. Go, get some water
And wash this filthy witness from your hand.