Susan Fleming birdied the third hole for the second straight day and finished with 80-11 -- 69 for a 36-hole net of 142 to win the Women's District Golf Association Keefer Cup by six shots yesterday at Chevy Chase Club.

Betty Looney, a 13-handicap golfer from Army Navy, finished second with 72 -- 148, followed by Peggy Widicus of Army Navy (12 handicap), 76 -- 151.

Before she teed off yesterday, Fleming witnessed an unfortunate soul seven-putting the sloping 10th green. WDGA President Julie Hemsing further demonstrated the danger by five-putting No. 10.

"I knew I had to be careful there," said Fleming, who moved to Arlington from Scotland four years ago and plays out of Bretton Woods. Fleming did three-putt the 10th hole for a bogey, but earlier had birdied the par-5 third hole after hitting a pitching wedge approach three inches from the cup. Her round was steady throughout.

Fleming, 31, started playing golf at age 9 and, after she played for the University of St. Andrews in 1972-76 (with historic St. Andrews as her team's home course), she lowered her handicap to eight strokes.

Fleming, whose previous best showing was winning the WDGA first flight title last year, said of her Keefer victory: "It's great. I really enjoy playing in the District."

Kim Williams of Bethesda Country Club, named to this year's Curtis Cup team, shot 80 and tied for low gross at 158 with present WDGA champion Brenda Baker of Hidden Creek (81). Inman-Hamilton Lead

Scott Inman from Springfield Country Club and partner Grey Hamilton from Tantallon Country Club shot a best ball 66 to lead the Belle Haven Four-Ball Invitational at Belle Haven Country Club yesterday after one qualifying round. The second qualifying round will be played today with the final rounds Saturday and Sunday.

The four-day event drew 156 two-man teams.