The German equalled the course record with a 64 on Thursday and while her second round scoring was not quite as spectacular she still registered a 69 to leave her three clear of Korea's Sun Young Yoo.
Gal recorded five birdies and two bogeys as she moved to 11 under for the tournament while Rebecca Lee-Bentham, who had been just a shot back overnight, fired a disappointing 76 that included a double bogey on the ninth.
Yoo was far more consistent as she fired a flawless second consecutive 68 to keep her two clear of the chasing pack.
American Gerina Piller played the low round of the day as her blemish-free 67 saw her move to six under alongside fellow American Cristie Kerr and Thai player Pornanong Phatlum.
Morgan Pressel, Anna Nordqvist and Hee Young Park were all a further shot back, one clear of a large group including world number one Inbee Park and American Solheim Cup players Lexi Thompson and Natalie Gulbis.
Further down the leaderboard, eyes were on 16-year-old Lydia Ko, the Seoul-born teenager who was making her bow as a professional after announcing last month that she would be leaving the amateur ranks where she enjoyed great success.
The New Zealander was the youngest person ever to win a professional golf tour event and the youngest ever to win an LPGA Tour event.
And she recorded a second consecutive 71 to sit two under alongside Michelle Wie.