Tara Nettleton, the widow of Australian Islamic State terrorist Khaled Sharrouf, has died in Syria from complications associated with appendicitis.
The former Sydney woman is believed to have died some time ago after she was unable to access life-saving health services.
It is believed that the mother of five was living in Raqqa with four of her children and one grandchild after the death of her husband as recently as last year.
Family friend Robert van Alst confirmed that Tara had died last year, but that her mother Karen Nettleton had only recently been informed.
Mr van Alst said the news of the death of her only child had left Karen devastated.
"She said it was the worst day of her life. And it was made worse because she could not be with her daughter when she was dying to give her comfort," he said.
Mr Van Alst told Fairfax Media that Karen said the second worst day of her life was knowing her grandchildren and great grandchild didn't have her there to look after them.
He and Karen are now most concerned about Tara's children, who are just "innocent Australian kids", he said.
Mr van Alst said Tara had suffered a related illness before she left Australia.
It is understood that she died from complications after having surgery for appendicitis.
Mr van Alst said that Karen had told him she felt for the first time the reality of the situation in Syria, and how the people who are
desperately trying to get out, must feel.
Tara's husband Khaled Sharrouf slipped out of Australia in December 2013 using his brother's passport and joined Islamic State, meeting up with his friend and fellow terrorist, Mohamed Elomar.
Tara and their children followed via Turkey soon afterwards.
Sharrouf achieved global notoriety when he tweeted a picture of his son holding the severed head of a Syrian solider captioned "that's my boy".
The photo, posted by a Twitter account then believed to belong to Elomar, spruiks him as the "young cub of the Islamic State".
In June last year, Karen Nettleton told Fairfax Media how she was watching television at home when she received a text message from Tara's eldest daughter Zaynab. The teenager had just become the widow of her husband Mohammed Elomar.
"Hello Nana, how are you? My husband got hit by a drone yesterday and got killed. When I found out I was happy for him to get what he wanted and go to paradise but at the same time I was devastated because I loved him so much and I knew I was never gonna see him again in this life."
Following the deaths of Sharrouf and Elomar, Karen begged the Australian government to let Tara - who converted to Islam and married Sharrouf a decade ago - and her children return to Australian
She said Tara was desperate to come home and has made the "mistake of a lifetime" by following the reviled jihadist to the Islamic State war zone.
Nettleton said last June her daughter and grandchildren were in need of help more than ever.
"[They] more than ever need the love and care of their family to help them recover from the trauma, abuse and terrors of war they have experienced," she said.
The Australian Federal Police declined to comment on Wednesday night and referred the matter to the Department of Foreign Affairs (DFAT).
DFAT has been contacted for comment.
