Montrage, 30, was part of a group of fraudsters in West Africa who tricked men and women into thinking they were in relationships with them, according to federal prosecutors.
She was charged with wire fraud and money laundering, among other counts. The most serious offenses carry a maximum sentence of 20 years in prison.
Montrage, who boasts more than four million followers on her Instagram page Hajia4Reall, even pretended to marry one of her victims to further her fraud, the Justice Department alleges.
"These scams can be both financially and emotionally devastating for vulnerable victims," U.S. attorney for the Southern District of New York Damian Williams said, announcing a six-count indictment against Montrage.
Prosecutors allege that the criminal enterprise operated between 2013 and 2019 and targeted "vulnerable" people in the United States who lived alone.
The alleged members would assume fake identities and then send emails, text messages, and social media messages that deceived the victims into believing that they were in romantic relationships with the sender.
The accused then allegedly convinced the victims to transfer money to bank accounts that were controlled by the alleged criminals.
Prosecutors say that Montrage duped several people, receiving more than $2 million in total.
Montrage allegedly used her real name with one victim, speaking to them several times by phone.
She sent the victim a tribal marriage certificate purporting to show that the pair had been married in Ghana, according to the prosecution.
The victim then sent her approximately 82 wire transfers totaling about $89,000 that were to purportedly help with costs associated with Montrage's father's farm in Ghana.
Montrage was arrested in Britain in November and was extradited to the United States on Friday. She pleaded not guilty in a Manhattan court to all counts on Monday.