Lindsay Davenport booked her place in the Wismilak International semi-finals by beating Maria Elena Camerin 6-3 6-1.
The US top seed was joined by Swiss second seed Patty Schnyder who saw off Aiko Nakamura of Japan 6-4 6-1.
China's Na Li won the battle of the unseeded players in Bali, coming through 6-4 3-6 6-2 against Alyona Bondarenko of the Ukraine.
Fourth seeded Francesca Schiavone rallied to beat fellow Italian and sixth seed Flavia Pennetta 5-7 6-3 7-5.
Davenport, who now plays Na lLi, admitted: "I'm still not exactly where I want to be.
"Some of the games I lost I still could have won, but I was mostly in control.
"I still feel I can get better and be more consistent. I did feel like I hit the ball well and hopefully I can get my range a little bit better.
"The one part of my game that I've felt really good about here is my serve. I feel like I'm hitting good first serves and if I'm not then my second serve is holding up."