"It was tough out there today," Barty said. "I didn't play my best tennis, but she didn't allow me to. I was out there giving it my all, but unfortunately just didn't come out on top today."
The oldest player in the draw, 41-year-old Kimiko Date-Krumm of Japan, lost to 2010 French Open champion Francesca Schiavone of Italy 6-3, 6-1.
Sixth-seeded David Ferrer of Spain and No. 8 Janko Tipsarevic of Serbia advanced in the men's tournament.
Later Tuesday, defending champion Rafael Nadal will begin his quest for a record-breaking seventh title at Roland Garros. On the women's side, 13-time Grand Slam champion Serena Williams was scheduled to be in action.
On Monday, Roger Federer was stumped only a short time after reaching yet another tennis milestone.
He had just won his 233rd match at a Grand Slam tournament, equaling the Open era record set by Jimmy Connors, and he couldn't remember who he beat to get that first victory.
