On her 30th birthday, which she celebrated in New York City, D'Arcy Benincosa did the wildest thing she could think of: she ordered a cup of coffee. The friend who was with her freaked out. They were Mormons, and coffee is forbidden; but both were on the brink of leaving the church. Later that day, Benincosa sampled a cocktail, and within a few months she had sex for the first time. "On my 30th birthday, I made the decision," Benincosa, now 34, tells me over the phone. "I'm done."

A teacher and photographer who lives in Salt Lake City, she is no longer active in The Church of Jesus Christ of Latter-day Saints. She describes herself as culturally Mormon and is one of more than 20 women who write for the Mormon feminist blog, the Exponent. Some of its contributors are still in the church, and it is part of a growing trend of Mormon feminist expression online.

Along with the Exponent, there are Feminist Mormon Housewives, Women Advocating for Voice and Equality (Wave), and a literary group called Segullah. In the past it was hard for Mormon women who struggled with the status quo to locate kindred spirits, but the internet allows them to find each other. When Benincosa came across the Exponent, she stayed up all night reading post after post. "I just cried because I thought, 'Oh my God, I'm not alone.'"

In the US, Mitt Romney's Republican bid has placed a spotlight on his religion (former candidate Jon Huntsman was also raised in the Mormon church). It is a patriarchal institution that has a fractured relationship with feminism: women are not eligible for the priesthood, although almost all men are; all leaders in the highest roles are men.

From a young age, girls are encouraged to believe they should marry and bear children. Pressure to find a husband can feel intense. "My roommates would make cookies every Sunday and give them to boys," Benincosa says of her college days. "That year, all five of my roommates got married. They were all between 20 and 22. I was the only one who didn't."

Yet in the 19th century, Mormonism was a radical and progressive religion, whose members worshipped a heavenly mother as well as a heavenly father. Even during the era of polygamy, Mormon women had careers and were among the first suffragettes. Margaret Toscano, a lecturer in Classics at the University of Utah, explains: "It was only in the 20th century that there was a conservative backlash and gradually from the 19th century until the 1970s, women's power was taken away from them."

The potential consequences for those who criticize Mormon doctrine are substantial. In 1993, a group of intellectuals were expelled, becoming known as the September Six. "After the excommunications in '93 it [feminism] really went underground and I was afraid it would disappear with my generation," says Toscano, who was disfellowshipped in 2000 for speaking out against the Church.

Still, feminist conversations quietly began to spring up, first on mailing lists, then blogs. The resurgence was gradual and many women wrote anonymously. "I was very scared to be perceived as anti-Mormon – I didn't feel that way in my heart," says Lisa Butterworth, who founded Feminist Mormon Housewives and remains active in the church. In 2010, Exponent II – a magazine founded by second-wave feminists, which had gone out of print in 2008 – made a comeback through the popularity of its blog. It now has a presence both online and in print.

Blogging suits Mormon practices because it draws on the tradition of keeping a journal, and church leaders have explicitly encouraged it – three years ago, Elder M Russell Ballard made a speech urging Mormons to use new media to share the Gospel. The church's official website, Mormon.org, is a pretty exceptional example of persuasive use of social media; and on the wider web a "Bloggernacle" flourishes, with conversations running the gamut from orthodoxy to dissidence.

All of this suggests the church may be willing to relax its stance on feminism. Dropout rates from Mormonism are high, with some estimates indicating that 80% of young people leave. By giving women a space to articulate their struggles, feminist blogs could stem that flow; but whether real change will occur on the issues feminists care about remains to be seen entirely.