New Zealand's lacklustre start and turnover count will still be of concern for Southby, however, as she contemplates next month's Constellation Cup series against Australia.
They committed 29 turnovers - 10 in the first quarter - in a scrappy final hit-out before their big challenge of the season.
Skipper Katrina Grant said while there is plenty for her side to work on heading into the four-test series against the Diamonds, she was happy with the progress made against Jamaica.
"Getting everyone on court was a key thing for us. It's all about building combinations and we were really happy to do that and get three from three," said Grant.
Southby opted for the same starting line-up that took the court in Wednesday night's second test, with Langman once again handed the wing defence bib. Shannon Francois started at centre and rookie shooter Te Paea Selby-Rickit at goal attack.
Once again this combination took a while to settle, as Francois and wing attack Grace Rasmussen struggling to find their connection.
A messy start in the shooting circle did not help. Bailey Mes spilled several passes and Selby-Rickit's shooting radar was off early on.
Jamaica took advantage of the bumbling New Zealand attack, leading for much of the first period before a late penalty goal from Selby-Rickit put the Ferns level at 13-13 at the first break.
After producing arguably their best quarter of the series, Jamaican coach Minneth Reynolds made the curious decision to change up her shooting end for the second quarter. Uncapped youngster Rebecca Robinson was thrown in goal attack, replacing the experienced Shenice Beckford.
Robinson's international debut lasted all of seven minutes, after the Ferns opened the second quarter with a blistering 11-3 run as they upped their workrate on defence to starve the Jamaicans of possession. Grant was particularly influential in sparking the defence to life, picking up four intercepts in the second quarter as the Jamaicans' were guilty of underestimating her speed and athleticism.
Robinson's replacement, Vanessa Walker, fared little better as the momentum stayed with New Zealand despite some fairly cynical defensive work being applied by the visitors.
Mes copped a particularly brutal hit from Shamera Sterling on the stroke of halftime, prompting the umpire to halt proceedings to issue Sterling a warning.
The Ferns shooter would have been consoled by a peek at the halftime score, with New Zealand taking a 15-goal lead on the back of a stunning 22-7 second-quarter effort.
Expected to revert back to her first-string line-up in the second half as she did in Wednesday's second test, Southby resisted widespread changes as she instead opted to give the alternate midcourt line a full game to develop their understanding.
The only change came to the shooting end, with Ameliaranne Ekenasio replacing Selby-Rickit, who shone in the second spell as she significantly upped her productivity.
Reynolds also made changes at GA, introducing Beckford back into the fold.
With the Ferns clearly in control, rookie shooter Maia Wilson got a chance and the 18 year-old responded well, sinking 10 of her 11 shots to help the Ferns close out a convincing 28-goal win.
