Olivia Mehaffey following her maiden US collegiate win in the

Arizona State's Olivia Mahaffey is brimming with confidence and "excited" for the rest of 2018 after claiming her first collegiate win in California.

The Royal County Down Ladies' star (20) finished as co-medalist in the prestigious Northrop Grumman Regional Challenge at Palos Verdes Golf Club.

Not only did she have an ace in a 68 to take the first round lead, holing a 19-degree rescue from 200 yards at her second hole, but she also added a level par 71 on day two to lead the elite field by a shot heading into the final round.

Strong winds made for tough conditions on the final day. But after a shotgun-start from the first, she battled to a two-over 73, making a clutch 16-footer across a slope for a birdie three on the 18th.

That left her tie with Texas' Kaitlyn Papp, who shot 72, and UCLA's Lilia Vu, who posted a 68, on one-under 212, two shots ahead of Stanford's Andrea Lee, the world No 5.

"I hit a good drive, then I had 150 into the wind and I was between clubs and my coach, and I decided to play the shorter club," a delighted Olivia explained. "It's my first win!"

After duly holing the putt, Olivia can look forward to a move up the world rankings having started the week ranked 12th behind international teammate Leona Maguire, who finished nine shots behind her in a tie for 18th.

"I’m excited," added Olivia, who was a key member of Arizona State's NCAA title-winning team last year.

"I’ve worked really hard and smart this winter. I feel like I’m progressing well. I love competing, so it's nice to get 2018 started."

After racking up eight top-10 finishes since she moved to Arizona State for the 2016-17 season, the elegant Banbridge native has made huge strides technically as she targets a career on the LPGA Tour after graduation in 2020.

"I hit it further now, and I strike my irons much better," she said. "I feel my swing is more solid. Also, I have a focus on skills and more competitive practice. I want to win and be in contention every event."

Winning individually leads to team success, and while Arizona State finished fifth behind UCLA at Palos Verdes, a successful defence of the NCAAs is at the top of Olivia's hit-list this season.

"My team goal would be to win nationals again," she said. "We have a great team who are gritty and can fight."

It was a rare off week for Leona Maguire who shot rounds of 75, 69 and 77 to finish 18th on eight-over with twin sister Lisa 41st after following a 74 with a pair of 76s.

The Duke pair return to action in the Darius Rucker Intercollegiate in Hilton Head from March 2-4 where Olivia and her Arizona State "Sun Devils" will also be gunning for glory.

Northrop Grumman Regional Challenge, Palos Verdes Golf Club, Cal. (Par 71)

Individual

T1 Olivia Mehaffey (Arizona State) 68 71 73 — 212
T1 Kaitlyn Papp (Texas) 69 71 72 — 212
T1 Lilia Vu (UCLA) 75 69 68 — 212
4 Andrea Lee (Stanford) 71 74 69 — 214
5 Bethany Wu (UCLA) 70 72 73 — 215
6 Lakareber Abe (Alabama) 73 71 72 — 216
7 Kristen Gillman (Alabama) 69 74 74 — 217
T8 Lauren Stephenson (Alabama) 74 68 76 — 218
T8 Chih-Min Chen (Oklahoma State) 70 74 74 — 218
T8 Mika Liu (Stanford) 72 72 74 — 218

T18 Leona Maguire (Duke) 75 69 77 — 221
T41 Lisa Maguire (Duke) 74 76 76 — 226.

Team

1 UCLA +15 292 284 291 — 867
2 Alabama +19 292 284 295 — 871
3 Stanford +24 295 292 289 — 876
4 Arizona +31 285 292 306 — 883
5 Arizona State +32 285 298 301 — 884
6 Texas +33 298 296 291 — 885
7 Florida +38 296 293 301 — 890
8 Duke +41 297 292 304 — 893
9 Washington +42 297 299 298 — 894
10 Southern California +48 295 306 299 — 900