Mary Kennedy admitted in court that her driving ability was impaired when she outside a school in Bedford, 30 miles north of New York City, in May.
Robert Kennedy, who has reportedly filed for divorce, was not in court. He also was not among the many relatives and friends who wrote supportive letters to Town Judge Kevin Quaranta.
"He was not asked," said Mary Kennedy's lawyer, Kerry Lawrence.
Robert Kennedy's mother, Ethel Kennedy, and his sister Kerry Kennedy wrote letters, with Ethel Kennedy telling the judge her daughter-in-law is "kind, loving, gentle and generous."
Mary Kennedy, 50, would not comment after the court session. Her lawyer said she was "pleased to get some closure."
The charge of driving while ability impaired is a minor violation and carries no jail time. The judge fined Kennedy $500, suspended her driver's license for 90 days and ordered her to attend two drunken-driving programs.
The judge also said Kennedy's psychiatrist must submit quarterly reports about her progress.
"You're going to have to live up to the continuation of your treatment," he told Kennedy.
"Absolutely," she replied.
The judge told Kennedy the letters from family and friends, including actor Dan Aykroyd and environmentalist Alex Matthiessen, praised "your life, your role as a parent."
"I hope we don't see you here again," he added.
Kennedy was arrested May 15 on a charge of driving while intoxicated after a police officer reported seeing her drive over the curb. Her only passenger was a dog.
Police said her blood-alcohol level was 0.11 percent; the legal limit is 0.08 percent.
The arrest came three days after Robert Kennedy filed a matrimonial action with the Westchester County clerk's office, naming his wife as defendant. Several news reports said he had filed for divorce, and most such filings are divorce suits, but the papers are sealed and both Kennedys have refused to comment. Lawrence would not comment Thursday night.
Robert Kennedy, a prominent environmental lawyer, is the son of Sen. Robert F. Kennedy and nephew of President John F. Kennedy, both assassinated in the 1960s. Mary Kennedy is his second wife. They have four children.
Robert Kennedy had two children with his first wife, whom he divorced in 1994.
Bedford police said in May that they had responded to the Kennedy home twice in the week before Mary Kennedy's arrest but no crimes had been committed.