The Wellington winner told lottery staff she'd been aware a first division prize was yet to be claimed, but it never crossed her mind she may be the missing winner.
She finally got around to checking her ticket on Tuesday and got the surprise of her life when Manners Mags & Lotto store owner Rex Rutherford told her the good news.
"My mind just went blank and I stayed very calm," she said.
The woman has opted to remain anonymous. She plans to do some travelling, but has no fixed plans for the rest of the money.
"There are just so many possibilities now," she said.