After 24 contestants (counting the ones that were eliminated in the CMTDARS Reunion Movie) were eliminated, Heather is the last contestant standing on "Total Drama". As a result, she gets the million, not long before Ezekiel steals it.
Heather is the best season winner in "Total Drama" history because she lasted longer than any other contestant, whether if she made it to the Final Three more than once, or being the only winner who didn't return after being eliminated (unlike Duncan and Owen, winners prior to her season).
Heather is the very first female to win a season on Cartoon Network. She even won a season on her own, since Owen won because of Izzy and Lindsay, and Duncan won by vote after he tied with Beth.