Theme: Lady Macbeth as Tragic Heroine

Act  1  Scene  5  lines 73-75

He that's coming
Must be provided for: and you shall put
This night's great business into my dispatch.
 

Speaker: Lady Macbeth
Speaking to: Macbeth

Brief description of the circumstances:
Lady Macbeth is convincing  her husband to leave all the death plans of King Duncan to her, because she is full of evil and knows what to do .
 
These lines develop the theme  that Lady Macbeth can be seen as the true tragic hero of the play           because she just wants what's best for her husband, a good and respectful life. But this can only be achieved by the death of the king  thus giving her the title of the tragic hero. This is tragic because she  is doing something wrong.