Karen Hill (née Friedman) was born in Nassau County, New York in 1947 to a Jewish family, the eldest of three daughters. In 1965 she was working as a dental hygienist, and after work she and Dana Shapiro, a friends of hers, would go to the Villa Capra in Cedarhurst at 488 Chestnut Ave. for drinks. It was there that she first met Henry Hill, while on a double date with Shapiro and Paul Vario, Jr.

After four months of dating they eloped and were married on August 29, 1965. Due to their young ages they were not allowed to be married in New York without parental consent, which neither the Friedmans nor Hills granted. They had first tried to wed in Maryland, but could not get a blood test right away. Henry, who had been been stationed in North Carolina when he was in the Army, remembered some of his fellow soldiers took advantage of the less restrictive matrimony laws of that state to get married, and recommended they proceed there. When in North Carolina, (which had no regulations about blood tests) the couple was married. The newlyweds returned to Karen's mother's house at 136 Roberta St in Valley Stream NY , where they lived upstairs in a large remodeled bedroom suite. The Friedmans finally agreed to give their blessing for Henry to marry their daughter if he would convert to Judaism and marry her in a traditional Jewish wedding. Although Henry's parents-in-law were satisfied by this, Hill would later admit after their deaths he lied to them about being a Jew; for the Mafia is a Catholic organization and both his parents were Roman Catholics.

The marriage was tumultuous, and both Karen and Henry were involved in drinking and drugs. Double adultery (where both partners cheat) was also a factor in their relationship. They officially separated in 1989, and Karen filed for divorce in 1990, but it was not finalized until 2002.

Karen and Henry raised two children, Gregg and Gina, first in New York and later in various locations while they were in the Witness Protection Program, including Nebraska, Kentucky, and Washington. Today Karen lives under a new name and runs her own business.

She was portrayed by Lorraine Bracco in the 1990 film Goodfellas. Bracco never met the real Karen Hill, but got the idea after reading the script to base her performance with heavy inspiration from the 1964 film The Stepford Wives, about a group of women who are apparently perfect and pretend as if nothing is ever wrong. Bracco saw in Karen Hill a sense of rationalizing every thing her husband Henry had done, partly out of love, but also out of greed for the lifestyle his criminal activities garnered.