(Chip Somodevilla/Getty Images)

ABC News’ TJ Winick and Anne-Marie Dorning report:

Kara Kennedy, daughter of the late Sen. Ted Kennedy, suffered a heart attack and died late Friday evening,  sources confirm to ABC News. She was 51.

In 2002, Kara Kennedy, the oldest daughter of Ted and Joan Kennedy, was diagnosed with inoperable cancer.

With her father’s help, she found a surgeon at Brigham and Women’s Hospital in Boston who removed a portion of her lung as part of the treatment.   Five years later, her mother told the Boston Globe that Kennedy was cancer free and was running five miles a day.

“My daughter was my best friend,” Joan Kennedy said today. “She stayed with me all summer long in Hyannisport. … We had a wonderful summer together.

“She was beloved by everybody who knew her. She was beloved by all of her cousins,” she said. “So many people have been calling me today and it makes me feel good to know how much everybody loved her.”

In August 2009, Kennedy gave a touching reading of Psalm 72 at her father’s funeral at the Basilica of Our Lady of Perpetual Help in Boston.

Ted Kennedy often prayed at Our Lady in 2003 while his daughter was being treated for lung cancer at the nearby hospital.

Kara Anne Kennedy was born February 27, 1960. She has two siblings, Teddy Jr. and Patrick, the former congressman.

She was a graduate of Tufts University and was a producer for VSA arts, a non profit organization founded by her aunt Jean Kennedy Smith.

She was also on the board for the National Organization on Fetal Alcohol Syndrome along with her cousin William Kennedy Smith.

Previously she was a producer for the television program Evening Magazine at WBZ-TV in Boston.

She was married to Michael Allen, a professional sailor, in 1990 and they had two children, Grace and Max.

On Aug. 12, 2009, she accepted the Presidential Medal of Freedom from President Barack Obama on behalf of her father who was terminally ill at the time.