Mother left "devastated" after her teenage daughter fled to Iraq to become an ISIS sniper.

Linda Wenzel was 15 when she ran away. Yes, the German teen had become withdrawn since her parent’s divorce, but her 2016 disappearance still made little sense to her loved ones. A promising student, Linda was typically pretty quiet, her friends said, not one to cause cause drama.

Yet when her mother, Katharina Wenzel, searched her room for an explanation, she found three things: a prayer mat, a receipt for a plane ticket to Turkey, and a tablet computer with a second, secret Facebook account.

According to The Times, Linda had been communicating with people in the middle east, sending messages. Among them, “Pray, the end is nigh”.

It’s believed that Linda Wenzel was among 20 suspected foreign female fighters who had barricaded themselves in a tunnel in the Iraqi city of Mosul earlier this month.

German weekly Der Spiegel reported that the pale girl with auburn hair was serving as sniper for the terror group, until she and the other women (from Germany, Canada, Chechnya, Russia and Turkey) were arrested when Iraqi forces liberated the city from ISIS rule on July 10.

“We found her with a gun in her hand next to her Chechen husband, who was then killed by Iraqi forces in a firefight. She said she had killed a number of our men in the battle,” an unnamed Iraqi counter terrorism officer told The Telegraph.

“I believe she was a Daesh sniper, but maybe her husband pressured her into it. She looked scared.”

While authorities have not confirmed that the Pulsnitz teen was fighting for ISIS, the Dresden prosecutor conceded she had been identified in Iraq and is receiving consular assistance.

According to The Times, Linda's journey to Iraq last July was made possible by a man whom she met online and soon fell for. He was working for a group affiliated to Islamic State and it's believed he radicalised her before arranging her trip to the middle east.

She had reportedly been learning Arabic in secret and had converted to Islam before leaving; to her parents, she'd passed it all off as a general curiosity about the religion.

“We didn’t think anything of it, and even bought her a copy of the Qur’an,” Katharina told RTL Television.

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Come July, Linda told her parents she was visiting a friend for the weekend, but instead stole her mother's credit card and purchased a ticket from Dresden to Frankfurt and on to Istanbul. From there she made the difficult overland journey to Iraq via Syria. This, the girl who just six months earlier had never even caught a train by herself.

In Iraq, that girl was handed to ISIS, and became Umm Mariam, an ISIS "jihadist bride".

After her daughter's disappearance last year, after she found the mat, the Facebook account and the receipt, Katharina said she had been left utterly shattered, blindsided by her own little girl.

“I am devastated by the fact that she was apparently completely brainwashed and persuaded to leave the country by someone," she told German media, "and that she managed to hide it from me.”