The 19-year-old, who is playing only her second Major, was never able to settle down in the third round, after two successive 69s in the first two rounds.
She did have four birdies, one on the front nine and three on the back nine, but two bogeys on front nine and another four on the return journey wrecked her card.
At two-under 211 for 54 holes, she is T-27 but eight shots behind co-leaders, Korea's Chella Choi (67) and American Danielle Kang (68) at 10-under each.
Both Danielle Kang and Chella Choi will experience the pressure of the final group of a major championship for the first time.