The glistening pearl earring, which is probably tin and not pearl, is meant to contrast with the soft blended shine of the girls lips, which was painted in sfumato, a technique that Vermeer excelled at. The eye will naturally fix first on the earring and then move to the lips, which are at the same level and just to the left. Your eye will then move to the girl’s eyes and then across to the yellow headband, and finally return downward to the earring. This active circular momentum keeps your attention fixed on the painting, continually absorbing and reabsorbing its contrasting and blending elements.
To me, I had a much greater desire to be a part of the scene than I felt when I saw Mona Lisa at the Louvre.
In this Vermeer's image the maid's gaze and parted lips seems to invite you as an acquaintance, perhaps as a friend, to share this moment of calmness. Dressed as she is, not a time of intimacy or romance, just as a fellow traveler in this world.
(Overworking my imagination, I guess.)