The video of Courtney Clenney assaulting Christian Obumseli in an elevator was played by prosecutors one day after the 26-year-old was arrested in Hawaii and charged with murder.
The suspect is known as Courtney Tailor on social media platforms, where she has more than two million followers.
“The defendant was aggressively attacking Christian,” Miami State Attorney Kathie Fernandez Rundle said of the 21 February video.
Prosecutors say that the couple’s two-year relationship was “extremely tempestuous and combative” and led to the suspect stabbing her boyfriend in the chest with a kitchen knife on 3 April.
“I’m completely shocked, especially since we were cooperating with the investigation and offered to voluntarily surrender her if she were charged,” her defence lawyer Frank Prieto told The Miami Herald after the arrest.
She was arrested on the Big Island, where her lawyer says she was at a rehabilitation facility being treated for substance abuse and post-traumatic stress disorder.
She was taken into custody by the US Marshals Service and will remain in custody pending extradition to Florida for trial.
Her lawyers had claimed the stabbing was done in self-defence but Ms Rundle said that the evidence countered her claims that her boyfriend was the aggressor in the fatal incident.
She had claimed that she threw the knife at the victim from 10ft away, which the medical examiner stated would not have caused the stab wound that killed Obumseli.
Investigators say that the stabbing took place while Ms Clenney was on the phone with her mother, Deborah Clenney, between 4.43pm and 4.56pm.
An arrest affidavit states that during the same period of time, neighbours called building staff to report a domestic disturbance
The suspect then called 911 and prosecutors say that Obumseli could be heard in the background saying that he was dying.
“Defendant Clenney is also heard saying, ‘I’m sorry, baby,’” according to the affidavit.
Police say that after the attack, her mother allegedly texted her and told her “not to say anything to investigators without an attorney”.
Authorities say that the couple had been dating for less than two years and that she had been arrested for domestic battery at a hotel in Las Vegas in July 2021.
Police in Austin, Texas, had also reportedly been called to their home on multiple occasions.
They had been living in the One Paraiso building in Edgewater, Florida, for several months, where managers had dealt with several domestic disturbance complaints and were moving to evict them, according to The Herald.
Police in Miami had been called to their apartment to deal with a domestic disturbance call on 1 April. Two days later, the suspect called 911 to report that the victim had been stabbed.