Heyman scored twice in two minutes to help Canberra come back from 1-0 down and earn just their second win of the campaign in Saturday's Unite Round action at Leichhardt Oval in Sydney.
In a battle between the league's two lowest-ranked sides, the Reds controlled the first half and opened the scoring immediately after the break when clever work from Mariah Lee down the right wing created an easy tap-in for Isabel Hodgson.
But then Canberra's forwards burst into life.
Heyman hit triple-figures in classic poacher's fashion, pressing the United defenders and forcing a mistake before gathering the ball and coolly slotting it home.
As if reaching the milestone took a weight off her shoulders, the former Matilda doubled-up just a minute later with a towering header that gave Adelaide keeper Annalee Grove no chance.
Midfielder Vesna Milivojevic iced Canberra's win with a stunner, blasting the ball home from outside the box on 64 minutes to give her side a 3-1 lead.
It was a convincing scoreline, but Canberra did not have everything their own way.
Adelaide's Alana Jancevski had a string of chances to open the scoring in the first half, with one curling effort from the edge of the box forcing a strong diving save from goalkeeper Chloe Lincoln.
Heyman, who made her debut in 2008 in what was then the W-League, has also played for Sydney FC, Central Coast Mariners and Adelaide on the way to wrapping up her century.
