The "One Last Time" singer went public with her budding romance with Miller earlier this month, after she was spotted kissing her "The Way" collaborator during a date night in California.
The pop star hit the prizegiving red carpet solo, leading MTV pre-show host Charlamagne Tha God to inquire about Miller's whereabouts.
Asked where her "boo" (boyfriend) was, Ariana slyly answered, "Being supportive. It's OK to be alone even when you have a boo."
The singer's confirmation comes after the new lovebirds were snapped getting new tattoos together at the famed Shamrock Social Club on West Hollywood's Sunset Strip.