TMZ reports the 70-year-old woman in the photo cooperated with the Los Angeles Police Department to prosecute Mathers, and now if convicted, she could face up to six months in jail.
Mathers has been criticised for 'fat-shaming', and she released an apology video soon after in which she revealed that the post was 'accidental', and actually intended for a girlfriend.
Los Angeles City Attorney Mike Feuer released a statement to the Los Angeles Times condemning Mathers' post.
"Body shaming is humiliating, with often painful, long-term consequences, " his statement read.
“It mocks and stigmatises its victims, tearing down self-respect and perpetuating the harmful idea that our unique physical appearances should be compared to airbrushed notions of ‘perfect’.
“What really matters is our character and humanity. While body-shaming, in itself, is not a crime, there are circumstances in which invading one’s privacy to accomplish it can be. And we shouldn’t tolerate that.”
Mathers has also been banned from LA Fitness, who reported her to police after the incident.