When Hadiya converted to Islam in January 2016, her father filed a report with the police, claiming that his daughter’s conversion had been coerced as part of an elaborate tactic by the Islamic State to recruit her to fight in Syria. Months later, she married a Muslim man, Shafin Jahan, adding to her father’s resolve to have his daughter placed in his custody, at the family home.

Hadiya, who was born Akhila Asokan and changed her name after converting, said she had converted of her own free will and did not even have a passport that would have enabled her to leave the country to join the Islamic State.

The high court of Kerala State, where the family lives, annulled the marriage last May, ruling that “a girl aged 24 years is weak and vulnerable, capable of being exploited.”

Hadiya, who then returned to her family home, has told activists and the courts that her father beat her and committed her to a yoga center, where she says she was tortured and forced to convert back to Hinduism. Hadiya’s father declined to comment.

Her lawyer, Haris Beeran, said on Tuesday that she was keeping a low profile. Worried about threats from right-wing Hindu nationalists, she filed an affidavit in the courts in February saying that she fears for her life.

Her husband, with whom she has been reunited, is being investigated by India’s National Investigation Agency, a government counterterrorism body, for possible links to radical Islamist groups. His supporters call it a trumped-up charge to derail the couple’s marriage in the courts by making it seem that her conversion was part of a larger jihadist plot.

“They have been married and forced to live away from each other for the past year, facing harassment from her family and the N.I.A.,” Mr. Beeran said in a telephone interview.