It was her fourth half-century in ODIs and she crossed the 1000 run mark in the process, becoming only the eighth Sri Lankan to do so.
For once, the hosts didn’t have to lean solely on Chamari Athapaththu’s broad shoulders.
However, the skipper returned to form with her 20th ODI fifty and stitched together an opening stand of 101 with Vishmi Gunaratne, who made a fluent 42.
That solid foundation allowed Hasini Perera, 44, and Harshitha Samarawickrama, 26, to consolidate before Nilakshika’s late fireworks took the innings from steady to sizzling.
Sri Lanka plundered 80 runs in the last 10 overs, with 16 coming off the final over as they finished with a flourish.
New Zealand captain Sophie Devine picked up three wickets, but may have missed a trick by under bowling left-armer Bree Illing, who extracted lively bounce and pace to claim two scalps in just seven overs.
The White Ferns will stay put in Colombo to face Pakistan on Saturday while Sri Lanka take on an in-form South Africa on Friday.