Ms. Mam helped draw millions of dollars to the cause of combating sex trafficking by enlisting support and attention from luminaries like Oprah Winfrey; Queen Sofia of Spain; the actress Susan Sarandon; and Sheryl Sandberg, the chief operating officer of Facebook, who along with Ms. Sarandon sits on the advisory board of the Somaly Mam Foundation. Her work has been highlighted by journalists, including Nicholas D. Kristof, an Op-Ed columnist for The New York Times.

The Newsweek article noted that in discussing her past, Ms. Mam said she had been “sold in the brothel” by a man she knew as Grandfather, who turned her into a domestic slave at a very young age, sold her as a virgin to a Chinese merchant and then forced her to marry a soldier at age 14.

But Newsweek, in its May 21 article, quoted acquaintances and teachers from her childhood in the village of Thloc Chhroy as saying they did not recall Ms. Mam’s being raised by the “grandfather” figure she describes, and one childhood friend said she remained in the village until she got her high school diploma. The article also notes that Ms. Mam herself made conflicting claims about when she was sold into slavery and how long she had worked in a brothel: At a White House appearance, she said she was sold into slavery at age 9 or 10 and spent a decade in a brothel, while in her book, she said she was trafficked starting around age 16.

Ms. Mam could not be reached for comment on Thursday.

In its 2012 annual report, the Somaly Mam Foundation said that it had raised more than $2.8 million in contributions that year, and that its affiliated social workers had made contact with 17,000 sex workers in Cambodia, Laos and Vietnam, distributing 750,000 condoms.

But some have questioned the group’s practice of using young women to press the cause of highlighting the horrors of sex trafficking. Pierre Fallavier, who said he advised Ms. Mam’s antitrafficking group — known by its French acronym, Afesip — said in emails to The Cambodia Daily that the group’s work illustrated aid organizations’ practice of using composite portraits of people they help in their zeal to raise funds.