Almost a day later she was fronting media after another remarkable round "“ a three-under par 69 at the Clearwater Golf Club "“ that sees her only two shots back from the leader American Anya Alvarez as she looks to defend her title.
Ko visited the hospital last night when she was violently ill with a stomach bug and she was low on energy today after not eating a meal for almost 24 hours.
"I was really sick overnight," said the World No.4 who was clearly jaded.
"At one point I was going to withdraw but luckily I didn't. It was a stomach bug and I went to the hospital this morning. They said it was something to do with my guts, they said that there was more wind in there than normal. I don't really know."
If they didn't look closely "“ Ko wasn't her chipper self - the local golf fans wouldn't have known anything was wrong as she got to a six-under par total.
Only one shot back are American Beth Allen (68) and South Koreans Baek, Kyu Jung Baek (69) and Seon Woo Bae (71) but Ko who once again attracted the lion's share of the 3891 gallery at the golf course.
She got off to a slow start but she got into her work with three birdies in four holes midway on the front nine. Suddenly the marketing campaign around the Kiwi of "˜Here We Ko Again' looked likely.
No one really knew how hard Ko was fighting to stay in contention.
"I thought that I would chop it out there today. But I gave myself some birdie opportunities and when I did I got most of them so I am pretty happy."
Also pretty happy in the media centre was Alvarez. The 24-year-old from Oklahoma, who has conditional status on the LPGA Tour in 2014, leads the final round of a tournament for the first time.
"I have never led a tournament before so this is pretty exciting," she said.
"But l have to keep my head in the game. I have 18 more holes to play tomorrow and I have worked really hard and I am very happy to finally be in this position."
Alvarez said she took advantage of most of the opportunities she had.
"I think the most important thing that I did today was stay calm even when I could feel I was getting excited that I was playing well. I kept telling myself you have another hole to go the round is not over yet and to stay focused.
The leader, who has a teaching professional as a father, wouldn't be getting in touch with her old man tonight.
"I try not to talk to my Dad too much during golf tournaments but he knows a lot about my golf swing. He knows a lot about my golf swing and he knows how to say the right things at the right time to keep me encouraged."
She is not sure how she will handle the pressure of playing in the final group with Ko and all the fanfare that goes along with that but she is excited to find out.
"I like playing in front of people"¦I just hope that they are kind enough to cheer for me when I hit a good shot too. [laughs] It will be fun tomorrow. I feel like I am ready to play really good golf.
Ko is two shots back from Alvarez but she is feeling comfortable with her position.
"Two shots can happen over a hole. You know you can make a birdie and they can make a bogey and that is two shots right there. I am just going to play my own game. She seems like she is playing really well. Obviously I am going to try my best to win."
The 16-year-old from Gulf Harbour Country Club hasn't thought too much yet about the prospect of defending her National Open.
"Maybe tomorrow [I will] if I do get really close, if I am in that position and I am leading. I just want to feel better.
Ko believed her experience of closing out a golf tournament and playing under pressure should work in her favour.
"I don't know how many people followed her today but I just want to concentrate on my game. If one of the people I am playing against feels pressure then I can't do anything about it. I don't know if that is called an advantage keeping to your own strengths and playing your own game.
Ko was looking forward to going home to "chill out" and hopefully eat something ahead of the final round tomorrow where she'll play in the final group at 11:55am alongside Alvarez.
"I think keeping the energy levels is going to be hard because I don't want to eat too much or too much rich stuff. I just want to start tomorrow really refreshed and relaxed."
A total of 54 players made the two-round cut which was made at a two-over par of 146 and three Kiwis make the final round in Cathryn Bristow, Caroline Bon and Ko.