Tappan Zee jumper's pals in shock

The former Bronx HS of Science teacher who died in a naked suicide plunge off the Tappan Zee Bridge with her boyfriend was an unassuming intellectual known for diligently pursuing her Ph.D. at Cornell, teachers and classmates said yesterday.

Alfa Choice -- whose boyfriend survived the fall -- had been going to the Ivy League university ever since she received a scholarship to pursue an undergrad degree in biology there.

"I was taken aback," said a classmate who'd known her four years. "It didn't seem like her at all."

Why the Bronx native would want to end her life remains a mystery -- but there were some signs she was struggling.

After years of overachieving -- including earning her master's in education -- she abruptly took a leave of absence in January.

A witness who saw Choice, 29, and Christopher Shears, 44, before they jumped said they calmly exited their car.

"Do you really want to do this?" the witness shouted.

Shears, also a Bronx native, muttered "yep" twice.

"You definitely saw the affection between them," said the witness.

Police are probing whether Shears actually pushed Choice after she had some last-minute hesitation, a law enforcement source said.

Shears is in critical condition and may be paralyzed, sources said.