Afshan Azad, 21, who played Padma Patil, a classmate of the teenage wizard in the blockbuster Hollywood films based on JK Rowling's children's books, feared for her life during the three-hour ordeal, Manchester Crown Court heard.
She was punched, dragged around by her hair and strangled by her brother Ashraf Azad, 28, who threatened to kill her after he caught her talking on the phone to her Hindu boyfriend on May 21 last year, the court was told.
During the row at the family home in Longsight, Manchester, which also involved her mother and father, she was branded a "slag" and a "prostitute", and told: "Marry a Muslim or you die!"
The actress, who now lives in London, had pleaded for leniency from the court, begging the judge not to jail her older brother. But Judge Roger Thomas QC sent him to prison for six months after he pleaded guilty to the assault.
Judge Thomas told the defendant: "This persistent attack was accompanied by serious and very hurtful abuse and threats. It must have been a miserable and frightening experience for your sister which, she suggested, lasted for about three hours or so.
"The background to this offence lies in the concern that you, and perhaps other family members, had about Afshan's relationship with a young man who was not of the Islamic faith."
Judge Thomas added: "This is a sentence that is designed to punish you for what you did and also to send out a clear message to others that domestic violence involving circumstances such as have arisen here cannot be tolerated."
Earlier, the court heard that the actress's family are devout Muslims but she had begun a "romantic relationship" with a Hindu man.
Richard Vardon QC, prosecuting, said: "Apparently that was a cause of some concern as far as Afshan was concerned. She realised her family would never accept the relationship."