Rachel Jeantel called the verdict "BS" and said Martin, 17, wasn't aggressive but someone who "loved his family" and was a good friend, CNN reported Monday.
Zimmerman, a Hispanic-American neighborhood watch volunteer, was acquitted Saturday of second-degree murder and manslaughter charges in the shooting death of the unarmed Martin, who was black.
Jeantel was a key prosecution witness in the case who was criticized on national television for her dress, weight, demeanor on the stand and her speech.
Jeantel also derided arguments the case lacked a racial dimension.
"It was racial. Let's be honest, racial," Jeantel told CNN. "If Trayvon was white and he had a hoodie on, would that happen?"
After calling police and being told by the dispatcher not to do anything, Zimmerman told detectives Martin began beating him when he approached and he shot Martin to save his own life.
However, Zimmerman didn't testify during the trial, and Jeantel said his defense was "acting like a punk" by trying to portray Martin as a deadly threat.
"If you were a real man you would have stand on that stage and tell what happened," she said, calling Zimmerman "weak" and "scary."
In Los Angeles, city officials Monday commended police for their response to violence arising from a protest of the verdict and warned as of Tuesday, there would be a crackdown on similar actions, the Los Angeles Times reported.
About 350 Los Angeles Police Department officers flocked the city's Crenshaw district after groups of youths broke away from a peaceful protest in Leimert Park, damaging vehicles, smashing windows, setting fires and attacking several people, including a television reporter and his cameraman. As of late Monday, at least 13 people had been arrested on suspicion of committing a number of offenses, the LAPD said.
At a news conference, Los Angeles Mayor Eric Garcetti blamed the violence on a "small group [that] has taken advantage of this situation."
While protesters have the right to disagree with the verdict, "people also deserve to be safe on the streets and in their cars," he said.
LAPD Chief Charlie Beck said officers would have a more aggressive position toward protesters beginning Tuesday.
"This will not be allowed to continue," Beck said.
In Oakland, hundreds of protesters clogged Interstate 880 near downtown Monday evening, blocking traffic both ways, the Times said. After protesters were cleared from the freeway, they went downtown, where multiple arrests were made, authorities said.