The 26-year-old singer discussed her challenging relationship with Miller and the rapper's ultimate death at age 26 in September in the August issue of Vogue.
Grande and Miller split in May 2018 after two years of dating, and Miller was arrested for drunk driving days later.
At the time, Grande famously clapped back on Twitter at one person who blamed her for Miller's arrest.
"People don't see any of the real stuff that happens, so they are loud about what they think happened. They didn't see the years of work and fighting and trying, or the love and exhaustion," Grande explained in the interview.
"That tweet came from a place of complete defeat, and you have no idea how many times I warned him that that would happen and fought that fight, for how many years of our friendship, of our relationship," she added.
"You have no idea so you're now allowed to pull that card."
Grande said she spent years worrying about and trying to help Miller, who struggled with substance abuse issues.
FOLLOW REALITY TV WORLD ON THE ALL-NEW GOOGLE NEWS!
Reality TV World is now available on the all-new Google News app and website. Click here to visit our Google News page, and then click FOLLOW to add us as a news source!
Miller ultimately died of an accidental drug overdose.
"By no means was what we had perfect, but, like, [expletive]. He was the best person ever, and he didn't deserve the demons he had," Grande said.
"I was the glue for such a long time, and I found myself becoming... less and less sticky. The pieces just started to float away."
Grande had voiced her love for Miller and her sorrow over his death in an emotional Instagram post in September.
"i adored you from the day i met you when i was nineteen and i always will. i can't believe you aren't here anymore. i really can't wrap my head around it. we talked about this. so many times. i'm so mad, i'm so sad i don't know what to do," the star wrote.
"you were my dearest friend. for so long. above anything else," she said.
"i'm so sorry i couldn't fix or take your pain away. i really wanted to. the kindest, sweetest soul with demons he never deserved. i hope you're okay now. rest."
Grande released her fourth studio album, Thank U Next, in February.
Copyright 2019 United Press International, Inc. (UPI). Any reproduction, republication, redistribution and/or modification of any UPI content is expressly prohibited without UPI's prior written consent.