I was re-reading some of John Wardley's book "Life After Nemesis" last night, and he stated on page 67 that John Burton's backstory for The Curse At Alton Manor was that Emily felt ignored by her parents as a child, and - if I am understanding it correctly - became consumed by hatred and evil spirits which killed her parents in response?
I personally wasn't crazy about this backstory, because it makes her sound evil and thus less sympathetic; I personally would adjusted the storyline to have her become infected with a disease (e.g. tuberculosis), her parents callously disregard her symptoms, have her tragically pass away, and her tormented soul continue to haunt the house in the afterlife (granted: this storyline is somewhat cliche, though).
P.S. Some riders were evacuted from the ride on Friday and Saturday; there is some backstage footage of the ride in the YouTube video that I posted a link to yesterday in the Ride Availability thread, if anybody is interested.