Monalisa Perez, 20, was convicted of second-degree manslaughter for firing a Desert Eagle handgun into the chest of Pedro Ruiz, 22, outside their home in Halstad, Minnesota.
Monalisa Perez and Ricardo Ruiz III were hoping to create a viral video - by stopping a bullet with a book.
The mother-of-two took a plea deal in December that will allow her to serve out half of her jail term in increments of 30 days per year for the next three years.
She has also been permanently banned from owning firearms.
"Me and Pedro are probably going to shoot one of the most unsafe videos ever", Perez wrote on Twitter prior to performing the stunt.
Norman County Attorney James Brue said that the sentencing was right for Monalisa and pointed out that she had "relied on the assurances" of her boyfriend that the stunt would be safe to carry out.
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The couple's YouTube channel had 218 subscribers at the time and included pranks like Perez feeding Ruiz donuts covered in baby powder. She was spirited away by her family after the hearing before reporters could ask questions.
The last moments of the video show Perez pointing the gun at her boyfriend's chest and firing a single round.
A few hours before the incident, Perez also tweeted that they were about to do their most unsafe stunt ever, adding that it was Ruiz's idea.
Perez spelled out her concern about the stunt on her Twitter account a few hours before the shooting.
The two ran a YouTube channel devoted to videos about their lives as young parents, as well as typical YouTube prank fare.
Perez called 911, but medics couldn't do anything for Ruiz. The video of the shooting was never uploaded and was submitted as evidence to law enforcement. "I love my cousin and miss him very much", she said through tears. The judge said he would say next week whether it would be made publicly available. Perez will only serve 90 days of the sentence, and the remaining 90 will be stayed for three years.
The sentence is below the usual minimum guidelines, but was allowed to stand on the grounds that the stunt was mostly Ruiz's idea.