It is clear that she is as confused as everybody else by her husband's strange behaviour during the banquet scene in Act III scene 4. However, she is quick to try and cover up his actions with a lie that attempt to explain away what he does and the strange apparition that only he can see. However, in their private conversation together, it is clear that she is angry, disappointed and frustrated with him for demonstrating once again that he is not a man, and for doing it in such a public environment. Note how she berates Macbeth:
O! these flaws and starts
(Impostors to true fear), would well become
A woman's story at a winter's fire,
Authoris'd by her grandam. Shame itself!
Why do you make such faces? When all's done,
You look but on a stool.
Note the way she deliberately tries to pour scorn on her husband, making him feel ashamed of his fears and worries. Thus Lady Macbeth's feelings of surprise, amazement but above all disappointment, frustration and anger are made evident. She desperately tries to hold the banquet together, but at the end has to ask the Lords to leave until her husband can regain control of himself once more.