Crown Prince Mohammed bin Salman, Saudi Arabia’s day-to-day ruler, has loosened some restrictions on women, lifting a ban on driving by women and allowing them into sports stadiums. Last month, he named a princess, Reema bint Bandar bin Sultan, as the new Saudi ambassador to Washington.

When asked on “60 Minutes” last year whether men and women were equal, Prince Mohammed said: “Absolutely. We are all human beings, and there is no difference.” Asked about guardianship in another interview, he said he wanted to “figure out a way to treat this that doesn’t harm families and doesn’t harm the culture.”

But rights advocates say guardianship makes women and men profoundly unequal and leaves a woman with little recourse if she ends up with a controlling or abusive guardian.

“They are trying to put an image out there that they are giving more rights to women, but if they really want to do that, they need to get rid of guardianship,” Ms. Carroll said.

Ms. Vierra moved to Saudi Arabia in 2011 to teach at a women’s university while doing research for a graduate degree, Ms. Carroll said. Friends introduced her to a Saudi businessman who had been educated abroad and seemed supportive of her ambitions. They married in 2013, inviting friends to a destination wedding in Portugal.

“At the beginning, it seemed really great,” said Ms. Carroll, who was the maid of honor. “He was charming and loving and generous and kind. She felt like she had met somebody who was on the same page as her.”

The marriage produced the daughter, Zaina, but eventually grew rocky. Ms. Vierra’s husband often lost his temper, shouting and swearing at her in front of Zaina, Ms. Carroll said. Ms. Vierra asked for a divorce, which men in Saudi Arabia — but not women — can grant by merely speaking a few words. For more than a year, he took no action on her request.