Pettersen shook off the miscue by carding eight birdies over an 11-hole stretch to end at 20-under-par 268, winning the Oregon event for the second time in three years.
She finished two shots ahead of Stacy Lewis, who registered a 4-under 68 to take second place at Columbia Edgewater Country Club.
Claiming third place at minus-17 was Lizette Salas, who ended the tourney with a 3-under 69, while Cristie Kerr's second consecutive 69 earned her a fourth-place showing at 16-under 264.
Caroline Masson (70) garnered fifth place one stroke further back.
Third-round leader Yani Tseng stumbled to a 6-over 78, settling for a ninth-place tie at 12-under 276.