She was suspended without pay for 30 days, after which she will be fired, police said.
Gross could not be reached for comment, and calls made to the Fraternal Order of Police seeking a response were not returned.
The first brawl she was charged with, according to a statement from the District Attorney's Office, happened Jan. 25, 2012. Gross was walking with her then-18-year-old son, whose name was not released, on the 900 block of Marcella Street in Summerdale when she demanded that he fight a 16-year-old boy. The brawl soon widened as several groups of young men began fighting.
The statement did not offer a motive for Gross' alleged demand.
The next incident occurred less than two months later, on March 16. Gross and her daughter were in her car near Loretto Avenue and Sanger Street in Northeast Philadelphia when the daughter jumped out of the vehicle to confront a 13-year-old girl and her 17-year-old sister.
As Gross allegedly yelled encouragement, her daughter, then age 14 or 15, started punching both girls in the face. The victims later said Gross kept screaming during the fight that she was an off-duty police officer and no one would get arrested, according to the statement.
Then last Oct. 23, Gross and her daughter had another incident, this time with a 14-year-old girl near Lincoln High School in Mayfair. The two approached the girl and - as Gross yelled encouragement - the daughter challenged the girl to a fight.
The 14-year-old girl later reported that Gross punched her twice; she suffered a swollen eye and abrasions.
Police spokesman Lt. John Stanford said Gross' actions "are what we are combating every day out on the streets."
He added: "We definitely don't want any of our officers encouraging this type of behavior."