Whitney Henriquez took to Instagram to voice her outrage at the actor’s appearance at the awards just two months after his defamation trial victory over ex-wife Heard.
Henriquez, who testified at the trial, wrote: “MTV you’re disgusting and clearly desperate! I really hope that none of the people that made this call have daughters.
“I stand with Amber Heard.”
In a clip played at the awards ceremony in New Jersey, the Pirates of the Carribean star was heard saying “I needed the work”, as his head was superimposed on a floating virtual astronaut body.
In subsequent virtual appearances he declared that he was available for “birthdays, bar mitzvahs, bat mitzvahs, weddings, wakes, anything you need… anything.”
He also claimed he was a dentist.
The surprise cameos also upset watchers, as Depp remains accused of domestic abuse by Heard despite his trial victory.
Henriquez has long supported her sister during legal proceedings.
During the court case, she told the jury about a March 2015 incident in which she claimed that Depp struck her in the back while at the top of a staircase.
After the jury verdict was delivered in Virginia on June 1, she wrote on social media: “I am so honored to testify for you, and I would do it a million times over because I know what I saw and because the truth is forever on your side. I’m so sorry that it wasn’t reflected in the decision made by this jury, but I will never give up on you, and neither will anyone who stands with you. Forever by your side.”
Heard was found to have defamed Depp in her 2018 Washington Post op-ed about domestic violence and abuse.
She was demanded to award him $10m (£8.4m) in compensatory damages and $5m (£4.2m) in punitive damages.
Heard was found to have a partial win in her case and was awarded $2m (£1.6m) in compensatory damages, but no punitive damages.