She is unsure whether there is enough virility to go around between herself and her husband, so she summons plotting demons to "unsex me here." This is her impassioned request to be freed of feminine frailty and imbued with manly drive. The unsoundness of this idea is clear from the beginning: even if she could somehow overcome her femininity, which she cannot, sexing her up would not make her a man. But the text suggests that she wants to be rid of her womanhood, which implies that she feels inadequate as it is. By asking to be unsexed here, she is saying that she does not want to be female any more than is necessary to reproduce children. She wants to escape from women's roles entirely. This desire comes from a place of pain rather than joy. As soon as she asks for this demon to appear, she begins to tremble uncontrollably, an indication that she is deeply troubled by what she has done. It is possible that she feels like a woman but wishes she could act like a man. Or perhaps she feels like a woman but wishes she could feel like a man. We can't know for sure because no one has ever asked such a thing of a demon. However, we can infer some things from her actions.