The Brooklyn woman who died during her 21st birthday celebration was “severed in half” in the horrific car crash on the Williamsburg Bridge, prosecutors said.

Amanda Miner was in the back seat of the speeding gray 2013 Infiniti G37 driven by her allegedly drunk NYPD traffic agent pal when she was thrown from the car onto the Brooklyn-bound lanes after the vehicle hit a barrier and a support pillar early Thursday, police said.

Stefan Hoyte, 26, who was off-duty, was driving about 50 to 60 mph on the 35-mph-speed-limit bridge when he lost control of the car at 3:14 a.m., hitting the support column with such force that the car split in two, prosecutors said.

Police found Miner, an aspiring social worker who turned 21 on Wednesday, “severed in half lying dead on the roadway,” according to a Manhattan Criminal Court complaint.

Hoyte and his front-seat passenger, identified by sources as 24-year-old Michael Camacho — also an NYPD traffic agent — survived with minor injuries.

Cops said Hoyte appeared to be intoxicated, with alcohol on his breath, watery eyes and “unsteady on his feet,” according to the complaint.

Hoyte told police he had two alcoholic drinks at a bar prior to the crash, prosecutors said.

A Breathalyzer test Hoyte took showed .103 — above the .08 legal limit, sources said.

Hoyte was charged with vehicular manslaughter, assault in the second degree and drunk driving, according to the complaint.

He’s being held on $100,000 cash bail and his next court date is scheduled for Tuesday, March 21.

Miner was a junior at Lafayette College in Pennsylvania and had spent the day before her life was taken viewing “Wicked” on Broadway and having dinner with her family.

“She could’ve changed this world, she changed mine. But now we’ll never see how far she could’ve gone,” her devastated mom, Virginia Cabrera-Miner, told reporters Thursday outside the family’s longtime South 4th Street home.