"A strong and fierce Maori woman, with a heart of gold, [she] only spread light and joy. She was living her dream here in Thailand and I and many others were so blessed to have met her.
"We are all taken back by this event. Its a shock and a heartache. We love her very much," Ms Gibson told NZME.
"We were all just cheering her on hours before, fit and fighting, and then celebrating.
"I've already had so much loss in my life... People had to give me the bad news five years ago about my parents, so for me being at the scene and then talking to her son just cracking, I'm broken."
Ms Brown won her fight by knockout in the third round. Muay Thai fighters are known for their fitness and use their fists, elbows, knees and shins to strike opponents.
A Ministry of Foreign Affairs and Trade spokesman confirmed the "tragic death of a New Zealander in Phuket as a result of an accident".
"Consular advice and support is being provided to the family in New Zealand," he said.