Lady Macbeth’s hopes to be king reflect a time in which a woman was measured by the success of her husband.

Lady Macbeth is definitely the stronger one in the relationship.  She convinces her husband that he needs to kill the king in order to become king himself, after she learns about the prophecies that were made about his future successes.

Lady Macbeth has to provide the strength for her husband, because she cannot advance without him.  At the time, women had fewer rights and privileges than men, and women were limited by their husband’s standing.  This was Lady Macbeth’s problem.  In order to become the wife of a king, she had to make her husband do what she wanted him to do.  She manipulated him into doing what she wanted.

When you durst do it, then you were a man;(55)

And, to be more than what you were, you would

Be so much more the man. (Act 1, Scene 7)

This was likely not the first time she had done that.  Since she wanted to be a more powerful woman, she needed a more powerful man.  Chances are she manipulated her husband throughout his career, getting him slowly to the point she wanted him to be.  As long as she pushed and prodded, he progressed.

The fact that Lady Macbeth was able to get her husband to kill Duncan, even though he was not at all interested at first, shows that she had a certain amount of control over him.  Even though women held a lessser status than men, she was able to pull the strings.  In their relationship, because she was more aggressive, she was able to get him to do what she wanted.  If he resisted, she just bullied him into submission.  This is shown by her reaction when he asks her what would happen if they might fail.

We fail?

But screw your courage to the sticking-place,

And we'll not fail. (Act 1, Scene 7)

Lady Macbeth hatches the entire plan, and makes sure he follows it to the letter.  When he does not remember to leave the daggers behind, she scolds him and returns them herself. 

The standing of women is reinforced by what happens after Macbeth becomes king.  Lady Macbeth goes to a lot of effort to get him there, but once he has the throne he stops listening to her.  She soon realizes she has created a monster, and he is going on a killing spree and there is nothing she can do to stop him.  As a woman, she has no actual power.  Her power is derived through him.  If he does not listen to her, and she cannot manipulate him, she is subject to his whims.  He will destroy her as he destroys himself.

Lady Macbeth’s vulnerability is clear in the fact that she loses her mind and kills herself.  She feels guilt for her part in the death of Duncan and the murders that came next.  She sees the blood on her hands.

Out, damned spot! Out, I say! One–two—

why then ’tis time to do't. Hell is murky. Fie, my lord, fie! (Act 5, Scene 1)

The blood is more than a metaphor to Lady Macbeth.  She realizes that she has no ability to control her husband.  Her only recourse is to kill herself, because as a woman she is powerless.