The Pepperdine junior shot a 1-under-par 71 Wednesday to extend her lead to four shots at the 25th NCAA women's golf championships.
Vargas has been content to pick her spots and leave it to others to fire at the pins.
'You can't force it,' she said. 'You can't go out there and say, 'I'm going to birdie every single hole.' It's a very challenging golf course. You have to keep it simple. It's fairways and greens and trying to make putts.'
Arizona State, attempting to add to its record six national titles, built a three-stroke edge on defending champion Duke in the team competition. The Sun Devils led by 11 shots at one point but frittered away their bulging lead down the stretch.
'I'm happy with how we played up until the last four holes,' coach Melissa Luellen said. 'One time I looked and we were 11 shots ahead and kind of getting comfortable. Sometimes the players can look at that and kind of coast along instead of staying in their plan.'
Even though the Sun Devils began the day a shot back of Southern California, they were stone-faced as they walked to the putting green after completing play, aware they had wasted the chance to take a substantial lead.
'The wind kicked up a little bit and the greens were getting firmer,' Luellen said. 'The conditions seemed like they changed within the back nine. I don't think we adjusted very well.'
Vargas, who held a one-shot lead after her opening 68, stands at 5-under 139 midway through the tournament at Ohio State's Scarlet Course.
Arizona State's Jennifer Osborn was the only other player under par, shooting a 73 to stand at 1-under 143.
'It was harder to hold greens if you were attacking pins,' Osborn said of the Sun Devils' late slip. 'We may have gotten a little bit (mentally) tired. But we still hung in there, we're still doing OK. That's the main thing.'
The Sun Devils followed an opening 4-over 292 with a 294 and were at 10-over 586. Duke improved five shots from a first-round 297 to get to 589.
'That's more like it,' Duke coach Dan Brooks said. 'It's not like we didn't show up yesterday; I just think we had a learning day. We learned some today, too. There are some greens that are getting a little bit firmer. They're behaving like you would expect greens to behave on a new course.'
The tournament is the first event at Scarlet since Jack Nicklaus oversaw a $4.2-million update and reconstruction of Alister MacKenzie's design.
Southern California was another two shots back in third place at 591, followed by Tennessee (593), Purdue and Pepperdine (596), Auburn (599), Florida (600), LSU (605) and California (606).
Tiffany Tavee's second consecutive 72 was the low round for the Sun Devils. Besides Osborn's 73, Azahara Munoz had a 74 and Alissa Kuczka a 75.
Duke, the No. 1-ranked team in the regular season, was led by Elizabeth Janangelo, who shot a 71 after an opening 77. Jennie Lee had a 72, Amanda Blumenherst a 74 and 2005 NCAA medalist Anna Grzebien had a 75.
First-round leader USC needed 300 shots after taking 291 in the opening round.
Vargas, a native of Colombia, didn't have a bogey in her first-round 68 but opened the second round by dropping a shot on the first hole after hitting her drive into the left rough and behind three trees.
'I was actually pretty calm,' she said. 'On this type of course, a bogey is not something real bad. You have to let it be and keep going and forget about it. You can't change what you just did, so you move on.'
She recovered with birdies at holes No. 4 and 16, skirting trouble the rest of the way by finishing with only two missed fairways.
Osborn's round featured an eagle on the par-5 14th. She hit a driver and 3 wood to set up a 10-foot uphill putt.
Florida's Tiffany Chudy shot a 75 after an opening 69 and was at even-par 144 along with Tennessee's Violeta Retamoza, who had the low round of the day with a 69.
Copyright 2006 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.