Factual error: The Crane mansion is supposed to be set above the village of Concord as listed in the ledgers, however, Nell answers an ad directing her to the Berkshires which are nowhere near Concord.
Factual error: The original and remake are both set in America, yet the outside shot of the flat at the start of the remake is in England. It is blatantly a 1920's London council flat, probably one of those in The Borough. The original 1962 film also contained British background details. Was this intended as homage to the original?
Answer: Another possibility is the spirits of the children. As long as Hugh Crain was inside the house, the children were trapped inside too. They could have called Nell because they needed her help in being set free.