She put it down to releasing the pressure valve after all the pent-up stress during her maiden games in Brazil. The body, she says, has a propensity to build up stress and then it suddenly relaxes soon after individuals' campaigns are over.
"I was talking to Shea McAleese as well. I think almost half of the [New Zealand contingent of ] Olympians were sick in the plane on the way back from Rio.
"Three weeks out of the Olympics I was feeling the stress with just all the nerves because you're always thinking about it, even if you're trying to distance yourself a bit."
She says the Olympics is "the biggest sporting event in the world so you tend to get worked up about it".
While she and her fellow canoeists are disappointed not to have got on the podium, they have come back happy and wiser for it.
"We're the happiest fifth-placed crew in the world," she says.
"We gave it 110 per cent. We did everything we could do so we're really proud of ourselves.
"We're thinking there's no event like it and it's a massive thing to cope with that sort of pressure so we've seen it now and see where it takes us from there."
Fisher says they didn't see much of Rio while commuting from the athletes' village to the lagoon as part of their daily routine.
"It's a beautiful country with stunning views," she says, emphasising she'll never forget the backdrop of the Corcovado mountain with Christ the Redeemer looking down on Lagoa Rodrigo de Freitas.
She only saw two mosquitoes in the entire time there and both at night, thus negating fears of the Zika virus which is found in daytime mozzies.
"I looked for Usain Bolt and Michael Phelps but they must have been hiding," says Fisher although she said hello to her idols, the triathlete Brownlee brothers, Alistair and Jonny, of Britain, and heptathlete Ashton Eaton, of America.
Fisher's got the bug and wants to lock in 2020 Tokyo Olympics. She doesn't mind going to one more after that but it's early days.
