Vu sank six birdies which were offset by a bogey on the 15th but she was well in control as she finished at 14-under overall to win at the Walton Heath Golf Club in Surrey, England four months after claiming the Chevron Championship.
By the time both golfers reached the 18th, Vu had a comfortable lead and easily found the fairway and green to finish with a birdie while Hull made par with a long putt despite initially finding the bunker.
Vu was barely given enough time to take in the moment amid applause before she was soaked in champagne by her friends, who promptly emptied the bottle over her head.
Hull had raised hopes of a first home winner since Georgia Hall's victory in 2018 when she signed for 68 on Saturday but an eagle on the 11th was not enough as she made four bogeys and just one birdie to finish with a final round of 73.