The 26-year-old rapper died on Friday of an apparent overdose and had reportedly been struggling in the months following his split from Grande.
The pair dated for two years before their break up in May and in June Grande became engaged to comedian Pete Davidson.
In the hours since Miller’s death was announced Grande’s social media accounts have been flooded with messages about the rapper.
While some had been sympathetic, others wrote cruel comments blaming the Side to Side singer for Miller’s death.
“This is your fault,” one person wrote, while another vile message read: “It’s crazy because you really did kill him.”
Grande, who is yet to comment publicly on Miller’s death, has since disabled the comments on her Instagram account.
A source told Entertainment Tonight that Grande is “devastated” and “very upset” by Miller’s death.
“Despite their split, Ariana had always been supportive of his sobriety,” the source added.
In May Grande fired back at trolls on Twitter after she was blamed for Miller’s drink driving arrest.
“I am not a babysitter or a mother and no woman should feel that they need to be. I have cared for him and tried to support his sobriety and prayed for his balance for years (and always will of course) but shaming/blaming women for a man’s inability to keep his s**t together is a very major problem,” she wrote.
“Let’s please stop doing that. Of course I didn’t share about how hard or scary it was while it was happening but it was. I will continue to pray from the bottom of my heart that he figures it all out and that any other woman in this position does as well.”
Miller was found dead at his San Fernando Valley home in California on Friday.
According to TMZ a male friend had phoned 911 for help but the rapper was pronounced dead when paramedics arrived.
Miller had been set to go on tour next month and just hours before his death had posted an Instagram story showing a vinyl record playing lyrics from his song So it Goes.
The rapper has been described as a “bright light in the world” in a statement released by his family confirming his death.
“Malcolm McCormick known and adored by fans as Mac Miller, has tragically passed away at the age of 26. He was a bright light in this world for his family, friends and fans. thank you for your prayers,” the statement read.