I think that Lady Macbeth is primarily feeling frustrated. Here they are, possessed of the king and queenship as was their plan, and Macbeth goes and sees a ghost at the table? Oh, great. (Ha!) You can see this with the way she deals with the guests:
Sit, worthy friends. My lord is often thus, / And hath been from his youth. Pray you, keep seat. / The fit is momentary; upon a thought / He willl again be well.
Backtracking much, Lady Macbeth? Uh, MUCH too much! Ha! You can also see this in the way Lady Macbeth scolds her husband after his "fit":
O proper stuff! / This is the very painting of your fear. / ... Shame itself! / Why do you make such faces? When all's done, / You look but on a stool.
She's sick of her husband acting like this, ... he's going to ruin everything! And, in fact, he does. But, um, her frantic hand-washing doesn't help much either.
She is feeling two things -- she's feeling scorn for her husband but, at the same time, she's still feeling ambition.
Lady Macbeth thinks her husband is a weak and vacillating man. She does not think he really has the toughness a man should have. When he shows that in front of everyone, she feels scorn for him.
But that doesn't mean she gives up on him. She thinks he's destined to be king and she wants some of that power. So she still feels very ambitious and therefore supportive of him because she wants the power she thinks he will get them.
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.