The New Zealander had a nervous wait before she could celebrate her victory – for the first time in eight years in a major.
When Lydia Ko had finished the final round at St Andrews, Lilia Vu, USA, was breathing down her neck.
The American needed a birdie on the last hole to reach a playoff, but her nerves failed her and instead she was noted for a bogey.
As a result, she finished tied for second, two strokes behind Ko, along with Yin Ruoning, China, Nelly Korda, USA, and Jiyai Shin, South Korea.
Lydia Ko, world number six, took her third major victory in her career and her first since 2016.
It's almost too good to be true, she says to AP.
World number one Nelly Korda was long in the running for victory but played herself out with a double bogey on the 14th hole and a bogey on the 17th.
Linn Grant became the best Swedish player after a good finish. She went around the final round in under par and finished also –1.
Grant went four under par in the third round on Saturday and came back strongly after a weak start with five over par.
I'm leaving here with a good feeling and a big pat on the back. It's not easy to gather yourself and keep going after shooting +5 on the first round, says Grant to Aftonbladet.
Linnea Ström became the next best Swedish player on tied 22nd place, a total of two over par.
Amateur Louise Rydqvist surprisingly mixed herself into the top contention during the second round. But the finish was a heavy fall with six over par on Saturday and four over on Sunday. She finished tied 60th.
