This is actually a very important scene for discussing and analysing the character of Lady Macbeth in this incomprable tragedy. Having abandoned herself to the forces of evil in Act I, and committing herself to murder and deceit, we rather get the impression that Lady Macbeth has bitten off more than she can chew when it actually comes to carrying out the act. Although it is she that has to goad her husband into seizing the opportunity and making his destiny a reality, when it comes to the actual murder, she finds that she is unable to commit regicide herself and is only able to lay the daggers ready for her husband to kill Duncan and then to besmear the innocent grooms with Duncan's blood, thus implicating them with the murder of their liege. Note what she says to us:
Had he not resembled
My father as he slept, I had done't.
This quote therefore indicates that conscience and moral scruples are not so easily disposed of as Lady Macbeth would like, and that she is not, as your question indicates, as strong and tough as she would like to believe.