“The sense they got was where I was turning my back on them,” Ms. Dadabhoy said. Her parents accused her of thinking that she was better than her grandparents and other ancestors. “You think what you have is better than what we have? You think you’re like those white people,” Ms. Dadabhoy recalled them saying.

There are few role models for former Muslims, and although the religion’s history contains some notable skeptics, very few of them are women. Today, Muslim feminists like Irshad Manji and Amina Wadud advocate more liberal attitudes toward women in Islam, but neither has left the faith. And many atheists resist identifying with Ayaan Hirsi Ali, the Somali-American (by way of the Netherlands) whose vehement criticism of Islam is seen, even by many other atheists, as harsh.

One group that seeks to bridge that gap is Ex-Muslims of North America, which had an information table in the exhibition hall. Members of the group, founded last year in Washington and Toronto, recognize that their efforts might seem radical to some, and take precautions when admitting new members. Those interested in joining are interviewed in person before they are told where the next meeting will be held. The group has grown quickly to about a dozen chapters, in cities including Boston, Chicago, Houston, New York and San Francisco.

One of the group’s founders who was at the conference, Sadaf Ali, 23, an Afghan-Canadian, said that she had once been “a fairly practicing Muslim.”

During childhood, she said, “I was always fairly defiant.” As she grew older, she struggled with depression, and she thought that praying more and reading the Quran would help. She became more religious and looked forward to a traditional life. “I thought my life was sort of set out for me: get married, have children,” Ms. Ali said. “I might go to school. I’ll have a very domestic life. That’s what my family did, what my forefathers did.”