Both players shot 70 in the third round to move to 17-under-par after 54 holes, while overnight Mariajo Uribe floundered, carding a 79 and slipping eight shots off the pace.
The Colombian has dropped back into a share of fourth place alongside the likes of world number one Yani Tseng, with Beatriz Recari alone in third, but still six shots adrift of the leaders.
Ko said she would attempt to stay calm as she went head-to-head against Shin for the title. The teenager beat the world number eight to the Canada Open at the end of 2012, and said she would try to use that experience in the final round.
"I guess I've played alongside her before so it does make it a little more comfortable," she said.
South Korean Shin said experience would not count for much in the run-in, saying: "I think she has enough experience too.
"She played great last week and last year too (in Canada).
"I know she's hitting it great and her putting is really good."