Lady Macduff is represented as being entirely housebound and dependent upon her husband. She is like a prisoner in her castle and confined to spending most of her time with children. She is weak and fearful. Her own little boy puts up a stronger defense against the murderer than his mother, suggesting that even an immature male is stronger than a female.
The Gentlewoman who is in attendance on Lady Macbeth has no power. She is completely subordinate to the Doctor, who treats her like an inferior. The Gentlewoman is depicted as simple-minded and fearful, nothing more than a personal maid. She exists as a character mainly for the Doctor to have someone to dialogue with and to provide him with information.
Lady Macbeth is intensely ambitious, but she is completely dependent upon her husband to fulfill her ambitions. She cannot become queen unless he becomes king. Furthermore, she is characterized as simple-minded when it comes the matter of assassinating King Duncan. Her husband knows that it is a tremendously complicated and dangerous matter which will not be "done when it is done." In his soliloquy in Act 1, Scene 7 he says:
But in these cases
We still have judgment here, that we but teach
Bloody instructions, which, being taught, return
To plague th' inventor. This even-handed justice
Commends the ingredience of our poisoned chalice
To our own lips.
He can imagine all sorts of possibilities. If he can become king by killing Duncan, others will get the idea of killing him. People are bound to suspect him of the assassination, and they will be hard to govern because they will hate him and pity their dead king. His wife can only see the problems involved in disposing of Duncan and cannot see all the complications that can--and will--result from that atrocity.
There is only one strong woman's part in Macbeth. Shakespeare may have written in the parts for Lady Macduff and the Gentlewoman because he felt the cast needed a little better "orchestration." Lady Macbeth is a memorable character, but she is blinded by her ambition and the direct cause of her husband's downfall. In the end she has fallen completely to pieces, while her husband remains resolute and courageous in the face of the invading army.