The 25-year-old star released her 'Club Future Nostalgia' remix album in August last year - which featured new twists on her original 'Future Nostalgia' record which dropped a few months earlier - and the 51-year-old singer made a guest appearance on the track.
Speaking to Zane Lowe on Apple Music this week, Dua said: "Honestly, I couldn't believe it. I couldn't believe it.
"I sat by my phone and I was literally holding my face pretty much. I was like, 'Oh my God, this is crazy. This is crazy.' I was just pacing around the room. Yeah, like, 'I've got it!' "
She explained how the collaboration came together, with her team initially contacting the No Doubt legend to "clear the sample" to use 'Hollaback Girl' on the LP.
She added: "The way it happened was so cool because we basically contacted Gwen and her team to try and clear the sample for 'Hollaback Girl,' for 'Club Future Nostalgia'.
"And I was like, 'Maybe we should just ask, put a feeler out, see if she wants to do something.' And she loved Mark Ronson's remix of 'Physical.'
"And she was like, 'I'd love to jump on this.' I'm like, 'Hell yeah, let's go. This is surreal.' It was just so exciting."
Dua loved working on the remix record, and she noted the impact of the coronavirus pandemic when it came to getting everyone on board.
She said: "It was such an exciting period, especially because it was that period of lockdown and the whole project came together because of everyone being at home.
"But it just made lockdown so exciting. I was just dancing around the house, listening to songs that I guess I've known for so long, that felt so new.
"So I was really just rediscovering the music in itself in a different way."