Only three minutes later, Manawatu spread again and standout centre Mala Faumuina dragged three defenders over with her for 12-0.
Wanganui were trapped in their 15m and when they tried to run it out, Kinloch just blew them off the ruck ball and picked it up for the third try.
Fears of a cricket score mounted as despite a couple of good one-on-one tackles, Wanganui could not stop Manawatu working off their rucks towards the tryline and lock Jaydah Sutcliffe got the last halfback pass to dive over for the fourth try in the 18th minute.
But Wanganui took a rare chance as they got a chip and chase into Manawatu's corner, turning the ball over with a penalty advantage, and flanker Mia Maraku took the tap and twisted through to score.
Manawatu replied five minutes before halftime after more sustained buildup, with reserve forward Kaea Boyd going blindside from the tryline ruck to score.
Wanganui's defence tightened up in the first 12 minutes of the second half, before Manawatu worked themselves into position for a penalty tap close to the line and Vavake forced her way through.
But with Kinloch being helped off to an ambulance stretcher with an ankle injury, the worst of a couple of Manawatu knocks, Wanganui kept having a go as a great run by first-five Te Amorangi Karaitiana saw the ball get spread out to halfback turned winger Mereana Kumeroa, who outstripped the cover defence and ran back to the posts for a Maraku conversion and 38-12.
Wanganui began to pull off some hard tackles and forced turnovers, leading to Karaitiana gliding through another gap and running to the posts back-to-back tries.
Manawatu re-established themselves as they again put the ball through the hands and sent Faumuina free to turn on the pace and run in to score.
A chip kick ahead was claimed by reserve winger Jashana Tetue-Teuawiri and she survived two tired diving tackle attempts, with no other cover coming across, to score from her inside her own half.
But Wanganui had the last say as winger Rangimarie Wroe's good run led to a penalty, and the home side worked the ball for Karaitiana to dive over for a double on fulltime.
Manawatu Development U18 Girls 48 (M Faumuina 2, B Wallace, H Kinloch, J Sutcliffe, K Boyd, N Tavake, J Tetue-Teuawiri tries; Laura Claridge 4 con) bt Wanganui U18 Girls 26 (T Karaitiana 2, M Maraku, M Kumeroa tries; Maraku 3 con) HT: 31-5.