The most fitting interpretation from the options provided is:
She reveals the fact that she is not capable of murdering someone.
This option highlights Lady Macbeth's internal conflict and emotional struggle. She realizes that the physical resemblance between King Duncan and her father is a significant barrier for her, leading to her recognition of her own limitations when it comes to committing acts of violence, despite her earlier ambitions and urgings for Macbeth to go through with the murder.