A judge yesterday tossed a one-year prison deal offered to a teenage girl accused of burning her ex-lover’s cat to death.

Judge Margaret Clancy, who had earlier approved the plea deal, said “nobody realized” at the time that reducing a violent felony charge to a nonviolent charge was illegal.

Prosecutors in July let Cheyenne Cherry, 17, plead guilty to attempted burglary and animal cruelty after investigators said her 14-year-old accomplice was the one who put the helpless Tiger Lily in the oven.

The judge yesterday said Cherry could plead guilty to a reduced charge and still be sentenced to a year in prison.

But Bronx prosecutors quickly pounced on the legal snafu to offer Cherry two years behind bars in exchange for a guilty plea.

That prompted Cherry’s lawyer, Danielle Follett, to accuse the prosecution of playing to animal-rights activists gathered in the courthouse.

“They are succumbing to public pressure,” Follett said.

Cherry is due back in court on Dec. 2.