"Sad day. My beautiful young cousin lost her battle to cancer," she wrote on her Twitter account. "My heart is breaking for her two little girls. Vicious disease."
The mother-of-three has been at the center of a storyline in which her sister-in-law, Teresa Giudice, orchestrated to expose the reality star once worked at the Elizabeth, New Jersey's Looker's Gentlemen Club.
October marks Breast Cancer Awareness Month.
The Real Housewives of New Jersey's reunion special continues this Sunday, October 7 on Bravo at 10/9c.