That broke the batting attack and they failed to find rhythm in next 13 overs, ambling through to 135 all out after 32.5 overs.
Realising this would not be comfortably defendable, Wanganui believed their only chance of winning was attacking from the get-go - setting what coach Dilan Raj described as one of the best attacking fields he'd ever seen.
The breakthrough came in the ninth over, courtesy of a tidy caught and bowled by Chloe Peters to dismiss Gemma Sims for 18, followed by a clean bowl of the incoming Kayana Jones-Dennis on the next delivery to put Peters on a hat-trick, which she did not complete.
A tricky diving catch, at full stretch and an inch from the ground by Watkin, again off the bowling of Peters, saw the key wicket of current Central Districts representative player Melissa Hanson fall for 20.
From there, another key wicket fell before drinks with Eden Stone, in her first over, picking up former Dutch international and ex-Wanganui player Esther Lanser leg before for three.
Buoyed by restricting Wairarapa's score in the first 20 overs and taking some big wickets, an upbeat Wanganui emerged from the changing rooms to restart the last 20 overs, once again setting an attacking field with two donning helmets in close.
The added pressure was rewarded in the 24th over, with Lucy Lawlor clean bowling Georgia Atkinson (28), and then on the third ball of her final over, Watkins removed Kate Simms (10), exposing Wairarapa's tail.
Rarely seen in Wanganui's bowling line-up, Mitchell stepped into the attack after a second no ball by Lawlor resulted in her early removal from the attack.
A great catch by Stone off Mitchell sent Karen Bracewell (22) back to the stands, leaving the home side requiring 14 runs from four overs with two wickets in hand.
Wanganui will rue a missed golden run out opportunity from Mitchell in the 37th over, which was still a maiden, before the heavens opened as the 38th began.
The wet weather possibly added to a couple of misfields, which left the Wairarapa tailenders requiring two to win off the final Mitchell-bowled over.
Dot ball, then a two and game over.
Post match, Raj said he was thrilled with the team's performance.
"Instead of relying on one or two players, as Wanganui has been guilty of in the past, we're relying on everyone and finding roles for everyone.
"We've really grown as a group.
"We saw more consistency in line and length from our bowlers today and the team's looking forward to their first home match against Hawke's Bay on Sunday."
