Webb, who began the day with a four-stroke lead over Wei Yun-jye of Taiwan, never saw her lead drop below three shots at Royal Sydney. She finished with a 10-under 278.
Wei shot 74 Sunday to finish second at 4-under 284.
Paula Marti of Spain and Minea Blomqvist of Finland, each with closing 69s, finished tied for third at 2-under 286. Brittany Lincicome of the United States and Shin Ji-yai of South Korea also finished with 69s and were another shot back tied for fifth.
Katherine Hull of Australia shot a 7-under 65, the best round of the day, to move into ninth place at 1-over 289.
Two of the highest-profile golfers in the field had disastrous final rounds. Laura Davies of Britain shot 77 to finish at 13-over, 23 shots behind Webb, while Natalie Gulbis of the United States had a closing 81 and finished at 14-over 302.
Webb, Davies and Gulbis are all scheduled to play next week at Royal Pines in the ANZ Australian Ladies Masters, which is being co-sanctioned by the Ladies European Tour. Webb is a five-time Masters champion and Davies has won the event three times.
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