Campbell opened the second round with a well-taken birdie on the 1st and a par on the next hole, to Alvarez's bogey, to lead for the first time.
Alvarez birdied the 3rd to even it up, then went ahead after a rare bogey from Campbell on the 5th. But she bounced back with a fine birdie on the par-5 6th and a par on the next to win both holes and go back in front. Alvarez showed her class, with two birdies, to lead with nine holes to play as the remarkable quality of golf continued.
The two young adversaries went shot-to-shot to par the next five holes before Campbell bogeyed the 15th to put Alvarez 2-up with just three holes to play. In keeping with the topsy-turvy nature of this extraordinary match, Campbell birdied the 17th for the second time to be 1-down with just the challenging 18th hole to play.
Alvarez sunk a testing 10 metre putt to halve the final hole and take the title after 36 holes of superb, pressure golf.
Earlier on Saturday Campbell defeated defending champion Chantelle Cassidy in the semifinal.
Campbell had been behind at some stage in all of her previous matches and made a birdie on the 14th before finishing the match in some style with an eagle on her favourite par-5 17th.
-In the men's final between the youngest golfers to contest the title in 122 years, Daniel Hiller, 16, (Manor Park) defeated Sam Vincent, 17, (Lochiel Golf Club) 6/5.