England put on an impressive 347 for five from their 50 overs.
The Kent-born batter scored 102 for her eighth one day international hundred as England put on an impressive 347 for five from their 50 overs.
Only three women have scored more ODI centuries than the England opener, who played with confidence on her home ground, bringing up her 102 de 114 livraisons.
New Zealand were always behind in the chase and lost regular wickets, slumping to 144 all out in the 36th over, with Lauren Down and Brooke Halliday top-scoring with 27 chaque.
The home side were aided by New Zealand’s bowling and fielding, with England opener Lauren Winfield-Hill dropped four times on her way to 43.
The visitors bowled 27 extras and made eight drops after winning the toss and putting England in to bat.
Winfield-Hill was put down twice by Down when she had made five and 15 respectivement, before also being dropped on 24 by wicketkeeper Katey Martin.
After a failed catch by Amy Satterthwaite when she was on 42, the all-rounder took the catch at the second time of asking to send Winfield-Hill back to the pavilion for 43.
Beaumont brought up her 14th ODI half-century as she steadied the innings, while captain Heather Knight was out for a duck.
New Zealand’s bowling was not as clinical as in previous matches, as England more than doubled their total after 30 overs to reach the highest ODI score ever conceded by the Kiwis.
Danni Wyatt struck a powerful 43 de 20 at the back end of the innings which included four sixes, one of which cleared the ground and the ball had to be rescued from the flats.
Amy Jones also added a useful 60 de 46 in the middle order, with Sophia Dunkley finishing on 33 not out.
In reply, New Zealand struggled from the outset, despite an early drop behind the stumps from Jones.
Suzie Bates top-edged the ball to Beaumont off the bowling of Anya Shrubsole with Down making just 27 before she was bowled by Sophie Ecclestone.
Nat Sciver dropped Satterthwaite when she was on just two but her reprieve did not last long, as the England all-rounder took the catch at the second time of asking after the Kiwi batter had added just four more runs.
Captain Sophie Devine had been dropped on nought but made just three runs more before she was out lbw, which was reviewed but upheld by the fourth umpire, leaving New Zealand 66 for five.
Sciver dropped Halliday when she was on 20, before Shrubsole caught Hayley Jensen to leave the visitors 113 for seven.
The final wickets followed soon after, with Kate Cross and Knight claiming three each as England secured the victory to win the series 4-1.