Shin entered the final round on Sunday with a five-stroke lead - and needed it. She overcame five bogeys to finish at three-over-par 75 at Dundonald Links and finished at nine-under 279 for the tournament.
The 33-year-old South Korean led from the front in Scotland but her last win on the tour was her maiden one in 2016, at the now-defunct Volunteers of America Texas Shootout.
"My first win didn't really feel like a win at the time. I didn't feel like I deserved it," said Shin, still wet after being doused with water during the post-round celebration.
"But this one definitely feels a lot different. This one feels like I earned it. I worked hard for it. I started working with my putting coach four years ago, and he asked me what my goal was. I said I needed to win before I retire.
"So I had been wanting it so badly in the last four years. I'm very, very excited."
The last LPGA Tour player to wait 10 or more years between official victories was American Vicki Fergon, who went 12 years and three months between wins at the 1984 S&H Golf Classic and the 1996 Michelob Light Heartland Classic.
Shin carded bogeys on holes six to eight before halting her slide with birdies on holes 10 and 12. She limped down the home stretch with bogeys at the 16th and 18th.
"I feel like I've done everything wrong, just wasn't hitting it like I was the last three days and was hitting it into bunkers, bushes, and it wasn't fun," Shin said. "With the three bogeys in a row, I thought, 'Oh, boy, I don't know where this is going to go.'
"But I hung in there and so I'm quite proud of myself. Very happy."
A Lim Kim shot a 68 to climb into second place at seven-under, two strokes ahead of Thailand's Pajaree Anannarukarn (74).
Kim, of South Korea, answered a bogey on the second hole with a birdie on the third. She rattled off four straight birdies from the ninth hole.
Germany's Esther Henseleit (73) finished in fourth place at 4-under for the tournament.
Australia's Hannah Green (70, 294) finished with a share of 31st place. Of the other Aussies, Grace Kim (78, 298) tied for 44th while Robyn Choi (74, 302) shared 56th.
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