A New York orthodontist pleaded not guilty Wednesday to an attack on her ex-fiance’s new girlfriend, who was stabbed by someone hiding in her car.

Minutes after the stabbing, the orthodontist showed up at the chaotic scene to offer medical help — only to be identified by the victim as her attacker.

Alika Crew, 41, was arraigned in Westchester County Court on charges of second-degree attempted murder, first-degree assault, second-degree assault and first-degree unlawful imprisonment related to the July 28 attack in New Rochelle, N.Y.

The 30-year-old victim had spent the night with her boyfriend at the house he still shared with Crew, though the two had broken their engagement. As the woman drove away, someone who was crouched behind the driver’s seat stabbed her in the left side of the neck, New Rochelle police said.

The wounded woman fled the car, pursued by her attacker, and her hand was slashed in a subsequent scuffle.

Video from a home surveillance camera shows the bleeding woman staggering on the suburban street. A passing driver stops to offer help at about the same time as the home’s owner steps onto her porch while talking to a 911 dispatcher. More neighbors approach, cautiously.

Then another woman comes onto the scene, dressed in a black top and tights. She walks toward the victim, saying, “I’m a doctor.”

“She’s lying!” the victim yells. “It’s her.”

The homeowner calls out, “You’re the one who attacked her! You ran away.”  Then, recognizing her neighbor Alika Crew, she tries to reassure the victim, confirming: “She’s a doctor. She’s a doctor.”

The panicked victim yells, “Please, please stop!” as the woman in black physically restrains her.

The homeowner later told a TV reporter that when she called 911, the dispatcher said the incident had already been reported — as a dog bite.

When police arrived, Crew was still on the scene, and she was arrested then.

The other woman was taken to the hospital with injuries that required surgery. Investigators say the weapon was a razor blade.

Crew is out of custody on $200,000 bail. Her next court date is Nov. 2.

Crew practices orthodontics at clinics in Queens and Stamford, Conn.