Hammond was behind after the swim, exiting the water in eighth place and 10.30 minutes behind Crawford, with Lester second and 30-39 age group entrant Shannon Proffit (Christchurch) in third.
But Hammond caught up as it became all about her and Crawford, with Lester dropping off the pace on the bike leg while fellow pros Tamsyn Hayes (Dunedin) and Wanaka-based German Simone Maier moved into the top four.
Hammond eventually grabbed a 23- second lead, overhauling Crawford with around 30km to go on the bike.
Both women remained strong through the run as it seemed Crawford was just picking her moment to close the gap and then pass.
But it never happened and Hammond, perhaps drawing on the knowledge gain from her former Wanganui running coach Alec McNab, gradually increased the margin on the second lap to finish 7.13 minutes ahead.
The delighted Hammond said she knew going in that she would be having to push hard after the swim. "Today there was no wind and I was able to settle into my rhythm and I really enjoyed it for the first time.
"I just chase, that's all I can do there's no plan."
Hammond said she was initially flustered because she had never raced that close to Crawford before and was wondering if she had used up too much petrol early on.
"I just tried to find my own rhythm and took the first 10km controlled and then tried to wind it up after that.
"Every year I race here I seem to have a very close race with someone, so you just have to stay in your own head.
"I didn't look behind me, I just focused on moving forward and getting the nutrition in," Hammond said.
"[The Wanaka crowd] is so special. It's hard to acknowledge people when you're hurting so much but I do hear it and I really appreciate it."
The men's race was won by Christchurch's Dylan McNeice in 8:38.48, becoming the first man to achieve back-to-back victories in what is described as "the world's most scenic long-distance triathlon".
The overall Challenge Wanaka Triathlon Festival attracts more than 2000 athletes.