The Penicuik woman beat Spaniard Noemi Jimenez at the second extra hole in a sudden-death play-off after the pair had finished tied on seven-under 206 following three rounds.
“It’s taken four years, so it feels brilliant,” said Turner, who carded rounds of 65-70-71. “Even better that I had to do it in a play-off as there were a lot of nerves in that last putt.
“In the past I have led after the first round and dropped away but this week I managed to keep hold of it.”
Turner’s triumph provided Scotland with its second success of the season on the LET’s development circuit after Heather MacRae was victorious in the Belfius Ladies Open in June.
Elsewhere, Connor Syme and Robert MacIntyre suffered mixed fortunes in their last-32 ties in the US Amateur Championship at Riviera Country Club in Los Angeles.
Drumoig man Syme followed up his first-round victory over world No 2 Maverick McNealy by beating another American, Ricky Castillo, 4&3, covering the 16 holes played in a brilliant six under par.
But MacIntyre’s title bid ended as the Glencruitten left-hander went down 3&1 to Dawson Armstrong of the US.
Still on the amateur front, Scotland will face Wales in a wooden-spoon decider after losing 10-5 to Ireland on the second day of the Men’s Home Internationals at Moortown.