Well, the first and second sets did have, effectively, 14 games whereas the third set only had 9 games so the absolute number would be less even if the rate of DFs was about the same.
But it's still quite a difference (about 1.5 per game as opposed to approx 0.5 per game).
Pleased for her. She had a nice run in the doubles last week, which must have been pleasant and helped.