Hillier carded a 69 to be six-under-par in the 54-hole Ladies European Tour (LET) event at the Evian Golf Club Resort

The 31-year-old West Australian had led after the opening day with a round of 67 but shot 71 in the second.

Koivisto, who fired a final round five-under-par 66, birdied the extra hole while Hillier could only make par

The win was Koivisto's first LET win and her first cut made in five appearances in the event.

"I've been putting so well the whole week and today I was hitting some good shots so I got the job done," she said.

Leonie Harm and Johanna Gustavsson tied for third position on three-under-par.