How does Lady Macbeth’s knowledge of her husband’s character help her to convince him that the murder plot should be carried out?

She knows her husband is, " too full o' th' milk of human kindness" to go through with the killing of Duncan. She decides that she is more of a "man" than her husband and decides that she must take control of the situation because her husband is too much of a "wussy" to carry out the murder.