The 21-year-old singer - whose real name is Ashley Frangipane - tragically lost a baby just hours before she was due to perform, and went on to give the "angriest" show she'd ever given.
She recalled: "I'm like, 'I have to cancel this show!' And everyone's kind of like, 'Well, it's Vevo LIFT, and it's three million impressions, so...'
"It's the angriest performance that I've ever done in my life.
"That was the moment of my life where I thought to myself, 'I don't feel like a f***ing human being anymore.'
"This thing, this music, Halsey, whatever it is that I'm doing, took precedence and priority over every decision that I made regarding this entire situation from the moment I found out until the moment it went wrong. I walked offstage and went into the parking lot and just started throwing up."
The 'New Americana' hitmaker admitted she "beat herself up" over the tragedy, and thinks it happened because of her "lifestyle".
She told Rolling Stone magazine: "I beat myself up for it. I think that the reason it happened is just the lifestyle I was living. I wasn't drinking. I wasn't doing drugs. I was f***ing overworked, in the hospital every couple of weeks because I was dehydrated, needing bags of IVs brought to my green room. I was anaemic, I was fainting. My body just broke the f**k down."
And before suffering the miscarriage, Halsey admitted she was worried about how her pregnancy would affect her career.
She recalled thinking: "What happens? Do I lose my record deal? Do I lose everything? Or do I keep [the pregnancy]? What are the fans going to think? What are the moms going to think? What is the Midwest going to think? What's f***ing everyone going to think?"
And the 'Badlands' hitmaker admitted she really wants children "more than anything".
She said: "I want to be a mom more than I want to be a pop star. More than I want to be anything in the world."
