After Willow is murdered, Bob asks Diana to stay in the house to keep his wife Anne company, but says that Diana will have to sleep in the murdered girl's bedroom as there is no other spare room. However, earlier in the film, Aunt Opal showed Anne her husband's old bedroom, which she suggests should be used for his future children, so there was clearly at least one unused bedroom in the quite large house.
When Anne was signing her name in the Armour family bible she wrote her name as Ann Armour. On the end credits of the movie the character's name is listed as Anne, not Ann.