EUGENE, Ore. — Duke star Amanda Blumenherst advanced to U.S. Women's Amateur semifinals today, beating Spain's Carlota Ciganda 4 and 3 at Eugene Country Club.

Blumenherst, the three-time national college player of the year, will face 15-year-old Erynn Lee of Silverdale, Wash., a 4-and-3 winner over Chelsea Stelzmiller of Placerville, Calif.

Azahara Munoz, the NCAA champion from Arizona State, and Belen Mozo also advanced, setting up an all-Spanish quarterfinal. Munoz routed Australia's Stephanie Na 7 and 6 and Mozo beat Whitney Neuhauser of Barboursville, Va., 6 and 5.

"Nothing is going to change. We still are best friends," Mozo said. "We can't change our attitudes. If (Munoz) plays better and wins, awesome."

Blumenherst, trying to win the event a year after a 1-up loss to Maria Uribe in the final at Crooked Stick, took a 1-up lead with a birdie on the first hole, then won Nos. 7-9 to take a four-hole advantage.

"It definitely helps to get out (well) early," Blumenherst said. "I can get in my own game and forget who I'm playing and just see how low I can go."

Blumenherst has played 48 straight holes in match play without trailing. She last trailed through 11 holes in her first-round match against Lizette Salas.

Ciganda, the 2007 Ladies British Amateur champion and 2008 Spanish Amateur winner, will join Munoz at Arizona State this fall.

Lee won four straight holes to pull away from Stelzmiller. Lee won the ninth hole to take her first lead, then took the next three, with only one birdie in the four-hole stretch. The 51st-seeded Lee is the youngest remaining player.

"I just told myself to stay steady and play my own game and have fun at the same time," Lee said.

Lee said she knows she'll be the underdog against Blumenherst and often studies her opponents, but said it won't be necessary this time.

"I know enough about her," Lee said.

Munoz shot a 4-under 31 on the front nine to take a six-hole lead. She went up by seven with a par on the 11th and finished the match on the 12th with a halve for par.

Mozo, a Southern California player, birdied four of her last six holes against Neuhauser, finishing the match with a birdie on the par-5 13th.

"If you start putting well the rest of the game will come along," she said.

Munoz said she has mixed feelings about playing her good friend.

"It's going to be awkward because I have to play her, but it will be normal because I'll be talking to her," Munoz said.

The semifinals are Saturday and the 36-hole final is set for Sunday.