Lewis' 65 was her second in two days at Stockton Seaview Hotel and Golf Club in New Jersey and gave her a commanding lead at 12-under 130 heading into Sunday's finale.
That total matched a two-round tournament record set by Amy Benz in 1996 and equaled by Denise Killeen in 2004.
Moving into second place at minus-6 was Anna Nordqvist, who fired a 4-under 67.
First-round co-leader Mika Miyazato stumbled into a seventh-place at minus-4 with a 2-over 73.
Swim Week Miami Beach 2014 [PHOTOS]