The "No Tears Left to Cry" hitmaker was left reeling last month after learning rapper Miller had died from a suspected drug overdose at his Los Angeles home. She had dated the 26 year old for two years before parting ways in early May.
Ariana bowed out of a planned appearance with her new fiance, comedian Pete Davidson, at the 2018 Emmy Awards days after the tragedy, with her representative revealing she would be taking "some much needed time to heal and mend".
However, the pop star has slowly started to return to work, and now she has been unveiled as one of the performers for the inaugural Barbara Berlanti Heroes Gala in Los Angeles on 13 October.
The event will benefit the F**k Cancer organisation, which aims to raise awareness about the disease and educate people about the importance of early cancer detection.
Singer/actress Kristin Chenoweth and comedienne Jeff Garlin will also hit the stage at the bash, where "Arrow" star Stephen Amell will be honoured with the Hero Award for his longtime support of the charity.
The gig marks Ariana's first since losing Miller.
She had previously been booked to help kick off the new season of hit comedy show "Saturday Night Live", on which Davidson is a castmember, but pulled out citing "emotional reasons" and was replaced by Kanye West.
SNL creator Lorne Michaels shared the news during an appearance on the Origins podcast last week, ends September 28, as Ariana told fans online she was having "a tough month".
"i'm trying to get my work done and get back to normal and it's hard and i'm human and tired," she wrote in response to a concerned Twitter follower. "sorry i let u in or worried u. i shouldn't have tweeted. i kno better (sic)."
Grande later added: "can i pls (please) have one okay day. just one. pls (sic)."