ET's Keltie Knight was backstage at the show, and caught up with Tish after the performance, where she opened up on why Miley performed at the VMAs after previously announcing that she wouldn't be.
"She didn't change her mind, it was just a last minute thing," Tish said. "Something opened up and she came to sing and I'm so excited!"
Back in July, Miley tweeted that there would be "no f**kin way" she'd be performing at the show after the first round of nominations was announced, and she wasn't among the list of artists up for contention.
However, she ended up being nominated for Song of the Summer and Power Anthem for her song "Mother's Daughter," although there's no confirmation on whether or not her eventual nomination is what changed her mind.
The 26-year-old singer stepped out to the awards show in Newark, New Jersey -- marking her first awards show appearance since news broke of her split from Hemsworth earlier this month -- and moments before hitting the stage, cameras showed Miley backstage with rumored girlfriend, Kaitlynn Carter.
An eyewitness tells ET that the two shared a few sweet moments behind-the-scenes.
The two were seen holding hands, and at one point, Carter even put her hand on Cyrus' butt, according to an eyewitness, who says "they looked very much like a couple."