Susan Cummings was born on July 21, 1962, in Monte Carlo, Monaco. She is a fraternal twin and has a sister named Diana. Their father, Samuel Cummings, was a billionaire arms dealer. The family later moved to the United States. Once they settled in the U.S., Samuel bought a large estate in Warrenton, Virginia, called Ashland Farms. This estate covered 340 acres and was quite luxurious.

Growing up in a wealthy family, Susan and her sister lived a life of privilege. In 2004, Susan sold the Ashland Farms estate for $4.9 million. After that, she and Diana moved to another large property known as LeBaron Farm, which was 450 acres in size. This new home was designed by the architecture firm Versaci Neumann Partners. The design of their manor house received recognition in the 2006 Washingtonian Residential Design awards.

On September 7, 1997, Susan Cummings shot her boyfriend, Argentine polo player Roberto Villegas. This happened in the second kitchen of her farm at around 9 a.m. Villegas was preparing to play in a polo tournament that day. The couple had significant tensions in their relationship leading up to this event.

Cummings reported to the 911 dispatcher that Villegas had become abusive and had threatened her with a knife. When the authorities arrived, they found Villegas with a knife across his arm. Cummings had cuts on her own arm, which the police believed were likely self-inflicted. Due to the circumstances, Cummings was arrested and charged with homicide.

Susan Cummings was represented by a lawyer named Blair Howard, who is known for his high-profile cases. On May 13, 1998, Cummings was convicted of voluntary manslaughter. She received a sentence of 60 days in jail and was ordered to pay a fine of $2,500. After serving 57 days, she was released from jail.