A few late worshipers trickled in and joined the circle, hastily removing their shoes and respectfully bowing in the direction of Sheikha Fariha, who had the bearing of a slightly bossy school principal. During the service, one man discreetly made to leave the room. Her eyes tightly closed, legs crossed and back straight, Sheikha Fariha snapped, “Where are you going?” The man jumped at being noticed and sheepishly replied, “To the restroom.” She dismissed him with a wave of her hand without ever opening her eyes.

Sitting on the floor of the main prayer hall was Juliet Rabia Gentile, 36, who has belonged to this order for more than a decade. “I was always interested in Sufi culture: music, dance, art and the works of the Persian poets Rumi and Hafez,” Ms. Gentile said. “It was definitely more of a cultural rather than spiritual interest at first.”

Her upbringing in New York City was Christian. “Initially, my family thought I was experimenting and it would probably go away after a couple of years,” she said. “Certain friends were surprised I’d become a Muslim, especially post-9/11.”

The group’s female leadership was a lure for Ms. Gentile, who is proud that American Sufism has cultivated an atmosphere of acceptance. “Our sheikha is an unusual product of American religious freedoms,” she said.

But she is also aware that Sufis are in a difficult position, both within Islam and within American culture. “Sufis nowadays are under attack and called heretics,” she said. “It’s ironic given all the Islamophobia, there’s been a surge of growth of interest. People just want to understand.”

Ms. Gentile doesn’t wear the headscarf outside the Dergah. “I can sense that the vibe here is changing,” she said. “Americans have reached heightened paranoia in the two years since ISIS emerged. People are becoming irrational.”

She said her fellow New Yorkers were less likely to be swayed by panic. But she is nonetheless wary. “Fear is a strong drug,” she said.