Amanda Miner was having the perfect 21st birthday.

The college junior, who was home for spring break, saw “Wicked” on Broadway, had dinner with family and then went out with her friends Wednesday night.

But the celebration took a horrific turn on the way home to Brooklyn, with the aspiring social worker killed when she was ejected from a car driven by her allegedly drunken NYPD traffic agent pal on the Williamsburg Bridge.

Miner was in the back seat of the gray 2013 Infiniti sedan as it sped from Manhattan to Brooklyn just after 3 a.m. Thursday, police said.

Driver Stefan Hoyte, 26, who was off-duty, lost control and slammed into a barrier dividing the inner and outer roadway before hitting a support pillar with such force that it ripped the car in half, police said.

Miner, a Williamsburg resident, was thrown from the wreckage and died at the scene.

“She’s gone, that’s the tragedy. My baby’s gone,” Miner’s mom, Virginia Cabrera-Miner, said outside the family’s South Fourth Street home Thursday.

“She was a wonderful girl. My youngest out of three,” the mom said. “We celebrated her 21st birthday yesterday, and I’m not going to see her graduate from college.”

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

Hoyte was charged with vehicular manslaughter, criminally negligent homicide and DWI, and cited for speeding, police said.

He blew a .103 on a Breathalyzer test, sources said. The legal limit is .08.

Miner, who studied anthropology and sociology at Lafayette College, was supposed to graduate next year.

“She was born and raised on this block. She was a normal teenager,” said a woman who works at a Laundromat on South Fourth Street and knows the family.

“That’s crazy. I can’t believe it.”

Miner’s advisor, Professor David Shulman, said in an e-mail to Lafayette students that Miner, “just radiated niceness; she had a great, winning personality,” campus newspaper The Lafayette reported.

When asked if she knew Hoyte, Miner’s mother said, “I don’t know who the driver is.”

Hoyte’s tearful mom Jeanette Hoyte, 51, said at the family’s Flatlands home, “What’s a mother going to feel? It’s hurtful. You hear something like that, it’s hurtful.

“You’re always sorry for things like that, because you have kids. You tell them one thing, but sometimes they don’t listen to you,” she said.

Jeanette called Hoyte “a good son” and a “good father” to his 5-year-old daughter.

She claimed Hoyte was not a heavy drinker, saying “sometimes he goes out and has no drinks. So I don’t know what happened.”

Hoyte, whose Facebook page is filled with photos of his gray Infiniti, was suspended from his job.

Additional reporting by Daniel Predergast, Larry Celona and Natalie Musumeci