Karla Giraldo told cops Monserrate cut her face with a broken drinking glass after he discovered she had another man's police union card in her purse, sources said.
Monserrate, a former cop, demanded to know more about the other man and why Giraldo accepted his Patrolmen's Benevolent Association card, a perk usually given to close friends or family, sources said.
"He was jealous. It was in her purse. He didn't like her explanations, and it got nasty," a law enforcement source said.
Hiram Monserrate's girlfriend pushes prosecutors to drop assault charges
Marcia Pappas, president of the state chapter of the National Organization for Women, told the Daily News Monserrate should not take office until the charges against him were resolved.
"Certainly if there's an indication that he's a perpetrator of domestic violence, the leadership in the Senate needs to take the appropriate steps," she said.