I'm sure the gentlewoman has heard Lady Macbeth talk about her part in Duncan's death. She refuses to incriminate her mistress.
That, sir, which I will not report after her.DOCTOR
Gentlewoman tell doctor that L.Macbeth says something but she will not repeat it to him
Doctor says you should tell me
Gentlewoman replies that she will not tell to him nor to any one because there was no one else to witness her speech