Debbie Martin, 61, had encouraged Jolie's decision to have a double mastectomy, reported Daily Mirror.
Martin's husband Ronald, who has been by her hospital bed since she collapsed at home on Wednesday, said, "She had a seizure and we took her to the hospital. They have turned off the life�support and her family is all here holding her hand. She is the love of my life."
"She's in a coma. It's breast cancer but I think it has spread everywhere," said Martin's brother-in-law Rick.
The 37-year-old lost her mother Marcheline Bertrand, 56, in 2007 after battling ovarian cancer.