In Shakespeare's Macbeth, Lady Macbeth is a woman with the intelligence and aggressiveness to lead, who is kept from leading. She is a capable woman in a male dominated world. She can only operate behind the scenes, so to speak.
We never even see her leave the castle. Like Lady Macduff, she is kept at home while her husband runs around performing momentous actions. Lady Macbeth is responsible for and relegated to domestic duties, like preparing for Duncan's arrival.
Furthermore, she is only even allowed to participate in decision-making before Macbeth is crowned king. Once Macbeth has the crown, he shuts her out of the decision-making process.
In short, then, if we assume Elizabethan attitudes toward women are reflected in the play, the character of Lady Macbeth suggests that women in Elizabethan England:
- were thought inferior to men and kept out of politics and the making of major decisions, unless they were somehow able to contribute behind the scenes
- were supposed to stay at home and cook and clean and prepare for guests
That is of course, with the exception of one woman: Queen Elizabeth, herself, although she had died by the time Macbeth was performed.
I can think of two things that, in my opinion, Lady Macbeth tells us about the role of women in her day.
First of all, women were expected not to be ambitious and aggressive. We can see this when she asks to be "unsexed" so that she can act in the way she wants -- so she can, presumably, kill Duncan herself. When she lets her ambitions get away from her, she goes crazy and kills herself, presumably because she has gone outside of a woman's "proper" role.
Second, I think we see that people accepted the idea that women could be powerful behind the scenes. I think that Shakespeare shows her doing this in an approving way -- I don't see this as part of showing she is evil.