Agnes "Aggie" O'Brien threatened to write a tell-all book about Mary Alice Dorrance Malone unless Malone paid her $250,000 a year for life and let her stay on at Malone's rental property.
O'Brien, 55, pleaded guilty Tuesday to sending Malone extortionist threats, part of a negotiated plea that keeps her out of prison.
"It's understandable, but it's criminal," lawyer Michael M. Mustokoff said of his client's actions. "You can't threaten (people) for money."
O'Brien had worked for a quarter-century for Malone, who breeds show horses on her 1,000-acre Iron Spring Farm in an exclusive swath of Chester County, Pa., near Philadelphia.
The 61-year-old Malone, a divorced mother of two, is one of the country's wealthiest women. Forbes magazine estimates her net worth at $2.2 billion and ranks her No. 144 on its list of richest Americans.
She is the granddaughter of Campbell Soup founder John T. Dorrance and remains a board member of the Camden, N.J.-based company. Campbell Soup Co., which was founded in 1869, is the world's largest soup maker.
O'Brien, a member of the area's social set before a mid-1990s divorce, is a horse trainer and caterer who had been renting a home from Malone for years.
According to Mustokoff, O'Brien put aside her businesses for months at a time to travel with Malone to Colorado, where the family skied, and to Florida, where he said O'Brien sometimes cared for Malone's mother. She cooked for the family during the trips and earned enough from Malone each year to support herself.
In January 2009, Malone sought to sever those ties and evict O'Brien from the house. The reasons remain unclear, although O'Brien's emails suggest she felt wrongly accused of something.
She described the barely-disguised Roman a clef she planned to write to embarrass Malone in the Dec. 21, 2009, "When the Soup Boils" email.
"Maggie (the fictional Aggie O'Brien) got her feelings hurt when she was wrongly accused and never allowed to defend herself," the email states. "She is not willing to be ... victimized by Alice (the fictional Mary Alice Malone) after 30 years of loyal service."
The email concludes: "Maggie has tried repeatedly to be understanding and fair and now she's just a character in a book."
Malone initially sought to settle O'Brien's complaints through lawyers to avoid publicity. But after calling in a second set of lawyers, she agreed to notify authorities. The FBI set up a sting, and O'Brien was arrested in July.
She remains free on bail, and, as part of her plea, is expected to be sentenced Aug. 30 to six years' probation. She must also stay away from Malone and her family.
O'Brien, who appeared in court with her gray-tinged hair hanging loose to her shoulders, had no supporters in court for her plea. She declined to comment as she left the courtroom.
Malone also plans to remain mum.
"She was extremely upset and angry," her personal lawyer, Tom Hogan, said before Tuesday's hearing.
Malone doesn't plan to testify at O'Brien's sentencing.
"She plans to stay as far away as possible," Hogan said.