An Islamic State group widow posted rare public criticism of the militant group's leadership. Above, A resident of Tabqa city touring the streets on a motorcycle waves an ISIS flag Aug. 24, 2014. Reuters/Stringer

It’s rare for those under Islamic State group control to publicly voice criticism of the extremist group’s leadership. But as the militants lost millions of dollars in recent months to a U.S.-led airstrike campaign, a widow's complaint that the families of dead ISIS fighters are not being properly supported financially spread across pro-ISIS social media, Voice of America reported Wednesday.

In her letter, titled “A Reminder to the Leaders of the Islamic State,” a woman identifying herself as al-Muhajirahm calls out the leadership of the group, also known as ISIS, for unfairly distributing funds. She is believed to be a Westerner who joined the group.

“Imagine that you’ve helped a sister who requested zakat [charity] two days ago, but you have ignored the sister who has been waiting a month before,” she wrote. “She cries every night, concerned about how to feed her children, as her husband is martyred. The tears that roll down her cheeks and the pain she suffers will be something you will be asked about and accountable for.”

Delayed payments may be attributed to ISIS’ recent financial troubles. Largely due to U.S.-led coalition airstrikes, the extremist group has reportedly lost millions of dollars as its oil infrastructure and transit routes have been targeted. Reports late last year indicated that the extremist group has resorted to slashing fighters' salaries to cut costs.

The letter was first noticed last month by the Middle East Media Research Institute, a Washington, D.C., group that tracks extremist media in the Middle East.

“Such criticism is almost never found in such a widely circulated document,” Anat Agron, a MEMRI researcher, told Voice of America. “In the past, [ISIS] members have publicly criticized aspects of life in the Islamic State; however, normally such posts were swiftly deleted.”

Women who have joined the ranks of ISIS are often used as incentives for male fighters, who are promised a wife upon their arrival. Dissenters have in the past criticized the treatment of widows, including how they are often forced to remarry immediately after their husbands are killed.