Factual error: When Griet is introduced to the camera obscura, far too much light is projected onto Vermeer's and Griet's faces. Camera obscuras don't make their own light; rather the image produced on the viewing screen is always dull.
Revealing mistake: When Griet has her left ear pierced in order to wear the earring for the portrait, the cloth covering her hair and ears stops just short of covering a well-healed hole in her already pierced right ear.
Continuity mistake: When Vermeer picks out earrings for his wife to wear, he selects two pearl earrings (same one later found on Griet). When he hands them to his wife, he gives them both to her, however when you look at Vermeer in the next shot he is holding one of the earrings.
Continuity mistake: When Greet is introduced to the camera obscura the props of a finished painting are present in the room instead of the props for the painting shown via the camera obscura.
Continuity mistake: Van Ruijven grabs Griet and makes her drop the plates she is holding. She bends down and picks up a broken piece of crockery and an unbroken plate. In the next shot, the plates she is holding are both unbroken. (00:58:00)
Answer: Obviously, since she married him in the end.