Why does Jaggers’ housekeeper remind Pip of something from Macbeth? How does she act?

Pip has seen a performance of Shakespeare's Macbeth and the housekeeper's face reminds him of the face that rises out of the witches' cauldron in the play, "I always saw in her face, a face rising out of the caldron." Pip begins to suspect that Molly is in fact Estelle's mother.