The original image featured the teenager tearing up a poster of a gun target, like those used at a firing range.
Taken for Teen Vogue and turned into a GIF, it showed Ms Gonzalez standing alongside three of her classmates.
They have been edited out of some of the doctored versions, and the gun target changed to the US constitution. Parts of Ms Gonzalez’s face have also been darkened to show shadows under her eyes, while her nose also appears to have been made broader.
There is a compelling short video of Emma González tearing up a target (used for shooting). Gun extremists have doctored the video so it looks like she's tearing up the Constitution. Some wacko might believe she did that! Propaganda like this is very dangerous to us all. pic.twitter.com/hKZmai1kAw
— Cornelia (@PaladinCornelia) March 25, 2018
It is unclear who created the new images or how many times they have been shared online.
The edited image and GIF showing Ms Gonzalez were posted anonymously on controversial forum 4chan.
They were later shared by several high profile figures on the right, including actor Adam Baldwin, who posted the GIF with the German hashtag #Vorwarts (#forwards).
The posts emerged on the same day as Ms Gonzalez – a leading figure in the gun reform movement that developed after the shooting at her Florida high school last month – took to the streets with hundreds of thousands of protesters across America to call for stricter gun laws.
While Mr Baldwin later defended the images as political satire, some Twitter users appeared to accept them as genuine.
“Watching Emma Gonzalez tear my Constitution in half make my blood boil!” wrote Anna Eddy.
— Anna Eddy (@AnnaEddy1) March 24, 2018
Others accepted they were fake, but approved of the symbolism.
“The picture of Emma Gonzalez is photoshopped, if you didn’t know,” wrote Irma Hinojosa. “It stands true as she is ripping the Constitution with her words… Be mad she’s rallying people to take away the right to defend yourself.”
Many others came to the teen’s defence and criticised those who were sharing the images.
“The right is passing around a photoshopped clip and pic of Emma Gonzalez tearing up the Constitution (she actually tore up a shooting range target),” wrote Hurst4Spd. “What this tells you is that they have no response to the substance of her message. So they've decided to lie about her instead.”
One user suggested people should follow Ms Gonzalez’s Twitter account and called for an end to attacks on the shooting survivors.
Since they first entered the global media spotlight in the days after the shooting, the students leading the charge for stricter gun laws have faced insults and accusations of dishonesty from some prominent figures defending existing gun laws.
Leslie Gibson, a Republican candidate for the Maine House of Representatives, called Ms Gonzalez a “skinhead lesbian” on Twitter and referred to David Hogg as a “bald-faced liar".
He later quit the race following widespread criticism.
Mr Hogg’s speech at this weekend's rally in Washington DC sparked a new wave of online attacks, with countless memes and videos now circulating online.
Some have compared a fist pump he gave at the end of his speech to the Nazi salute.
Others have suggested he looks like Adolf Hitler and has similar mannerisms and speech style.
“David Hogg is Hitler,” wrote one Twitter user alongside a picture of Mr Hogg with his fist held aloft, doctored to include a Hitler-style moustache and a Nazi armband.
However, the comparisons to the Nazi leader and doctored images were criticised by some people who opposed gun reform.
"I disagree with Hogg's view on gun control but you're literally comparing him to Hitler and that is insane," wrote Sarah Rumpf, who described the comparison as "vile".
She also spoke out against the fake images of Ms Gonzalez, writing, "I sure as heck don't endorse making up lies to attack these students."