Do you think Lady Macbeth would have acted sooner to cover Macbeth's suspicious comments at the banquet table if she'd known of
Macbeth's plan to kill Banquo in Macbeth?
Do you think Macbeth made the right choice in not telling her?
His decision not to tell Lady Macbeth is the right decision for him. Macbeth feels that he has to prove to his wife that he can do it all by himself. In Act I, scene 6, she had taunted him when he told her he wasn't going to go through with killing Duncan. "When you durst do it, then you were a man;..." There is nothing worse for a man like Macbeth than to have his manhood questioned, especially by his wife. This is his way of honoring her and showing her that he could plan and execute the murder of his good friend, and he has done it in the name of love. I did it for you, he is saying. I want you to be surprised and pleased.
Despite her lack of knowledge as to the reason for her husband's strange behavior, you've got to admit that she acted quickly to explain it to the gathered thanes. Even if she had known of Macbeth's actions, neither of them could have foreseen Macbeth seeing Banquo's ghost. Macbeth and Lady Macbeth know each other very well. They make a great team, unfortuantely they team up for evil.
Lady Macbeth is a smart cookie. In III, ii, Macbeth says to her:
Thou know'st that Banquo, and his Fleance, lives....
There's comfort yet. They are assailable.
...there shall be done a deed of dreadful note.
So, though Macbeth tells Lady M to "Be innocent of the knowledge," it isn't impossible to imagine that she gets his drift about killing them. And in III, iv, when the murderer appears at the door with blood on his face, it isn't too far-fetched to imagine that, if she didn't know before what has happened, that she does now.
The thing that she doesn't get right away is that Macbeth sees Banquo's ghost. This, potentially, isn't necessarily because she doesn't know that the murders are being committed, but that Banquo's ghost is invisible to everyone but Macbeth, so she doesn't know exactly what it is that he's reacting to.
...Please't your highness
To grace us with your royal company.
The table's full.
Here's a place reserved, sir.
Here, my good lord. What is't that moves your highness?
Thou canst not say I did it: never shake
Thy gory locks at me.
Gentlemen rise; his highness is not well.
Sit worthy friends. My lord is often thus.
She seems right on top of it when it happens, but her cover is not exactly very convincing, maybe because Macbeth's behaviour is so telling that it is nearly impossible to "cover it." Until he mentions "shaking thy gory locks," she doesn't realize what's happening because his comments about the table being full are merely puzzling, not revealing of what he sees.
So, I wouldn't be so quick to assume that Lady Macbeth doesn't get Macbeth's drift about murdering Banquo, and I also wouldn't be so sure that there would have been any time "sooner" to react to what was going on in the banquet.
I do think that Lady Macbeth would have acted sooner to cover Macbeth's suspicious comments at the banquet had she known that Macbeth was involved in killing Banquo. When Macbeth first begins having his "outbreak," Lady Macbeth is not sure what is happening, so it takes her a little bit of time to piece things together and then a bit more time to concoct a story that will be well received by the others at the banquet. That said, it does not take her long to put together what is going on, and she does a pretty good job of covering up for Macbeth and getting everyone out of the banquet hall.
Macbeth leaves Lady Macbeth out of his plans so that he can follow what he thinks is the right thing to do; however, in going about things on his own Macbeth does not have a second person to suggest whether or not his actions are warranted. Lady Macbeth encouraged him to kill King Duncan, but she possibly would have prevented Macbeth from killing so many others.