She made an eagle, two under par, on the last hole and before that had made six birdies but also three bogeys.
Sagström finds it difficult to interfere in the battle for victory.
Going into the final round, Canadian Brooke M Henderson leads at 17 under par, two ahead of South Korean Ryu So-Yeon and four ahead of American Sophia Schubert.
Henderson is nine strokes ahead of Sagström.
Anna Nordqvist, who was the best Swede on the first two days of the French competition, dropped six places to share 22nd place after a round of 70.