Delevingne, 22, met 32-year-old Vincent back in December and has since been following her around the globe on her tour, reported Ace Showbiz.
"They made no effort to hide their affections," a source said.
In a video posted by another fan on Instagram, Delevingne was seen caressing Vincent's neck and shoulder while Taylor Swift and Ellie Goulding were dancing behind them at BRIT Awards.
The model recently tattoed Vincent's real name initial 'AC' on her ring finger.
Neither Delevingne nor Vincent has commented on the report yet.