A student in Dundee, Scotland, was scared to discover that the secret doppelganger spent two years re-creating his social media station, according to her sister.
In Facebook, Linzi Cowan said that the look-alike reinstated poses, clothing, and even headlines her sister Chloe Cowan had posted on Instagram.
She said that the secret user even acted on the video, the scenes from Chloe's photo and her father, who has since passed away, according to the Daily Mail.
The post was split 11,000 times before it was deleted in the afternoon.
Police Scotland has told MailOnline that they can not confirm whether the incident was reported at either Dundee or elsewhere.
It is not clear who the Instagram is or what its motivation might be.
Chloe's sister Linzi has revealed the unusual online behavior of Chloe's alleged dualist to alert people to "the dangers of social media."
Her Facebook post reads: "Do not even know where to start with this, but you just want to let people know the dangers of social media.
"My sister Chloe is at Dundee University, and the other girl living in Dundee (who was aware of my sister until this week) has been activating her life on the instagram for nearly two years.
"This little girl's behavior is extensively reenacting a photographic album video that Chloe published about my father who passed (this gives me a trembling when I think about it).
"This girl did not follow my sister on social media and made a fake account to beat her without her knowledge.
"Her behavior is wrong and I just wanted this out in the open to make people aware of how frightening social media can be.
"My sister should not be hiding in her every move taken by another girl! Imitation is flattering, but this is too far away!"
Linzi shared a series of photos as compared to Chloe's original Instagram posts with those from the copy.
In one, Chloe is posing in a small black dress, sporting Mickey Mouse's ears and holding the reindeer.
In the replica she looks not only to copy her ears and stomach and wears a similar dress, it also represents the same left-foot forward pose and even uses the same title: "social life wu can not be seen", including "poo" emoji which Chloe uses in the original.
Another picture from Chloe shows her wearing black jeans and flip-floped shoes with a bordered black tip.
She leaned to her right with a lace and her right hand to her head. Copycat replicates the clothes and poses with dreadful accuracy – adding almost identical title.
The Linz Facebook post was divided more than 11,000 times after yesterday's announcement, but today it has come to the attention of the national media house around 3.30pm.
An Instagram account copy, "honeybasra18xo", has also been deleted.
Police in Scotland in Dundee told MailOnline that they did not have a record of any crime reported, but he believes a woman lives in Glasgow.
The Glasgow police could not confirm whether the incident was reported to them.