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The 18-year-old Dunedin skater finished her routines at the event - the second junior grand prix of the 2013-14 season - by recording a personal-best 72.97 points to finish in 23rd place overall.
But just making it on to the ice for the start of the routine was beyond three of her rivals, due to the altitude of Mexico City, more than 2000m above sea level.
''They had oxygen tanks and ambulances all on stand-by because people were dropping like flies,'' MacGibbon said.
''When I got off [the ice], they asked me if I needed it, but I was like [deep inhale], 'I'm fine'.''
Her career-best performance was in front of tough judges which, combined with the challenges of altitude, pleased MacGibbon even more.
''The altitude was crazy. There were a few people who pulled out because they didn't think they could do it.''
The result places MacGibbon in a good spot before the New Zealand figure skating championships in Dunedin from September 28 to October 1, when her aim is a top-two finish. That would give her enough points to get to the Australian championships in December and another junior grand prix event next year.
Her long-term aim is to make it to a world championship, rather than the Olympics, as she has one eye on a career outside skating, after she completed Correspondence School last year.
''To go to the Olympics, I'd have to keep skating until I was about 25, so maybe not.
''I want to do medical school when I finish [skating].''
MacGibbon's medical interests lie in pathology and working in intensive care.
One of the areas MacGibbon has been working on with Russian coach Fanis Shakirzianau is the cosmetic side of figure skating.
''We've been trying to do lots of arms to make me have more emotion with my skating, which is really hard when you're trying to do your jumps and being all emotional.
Gym work and more work on speed is the plan for MacGibbon in the next few months.
''Definitely my speed, and we've been working on my second mark, which is my components - transitions, skating skills and arms.''
MacGibbon has become used to training alone, which had her prepared for her solo trip to Mexico, without her mother, Jennifer Keen, who has supported her daughter ever since she started figure skating in Gore 11 years ago.
''I think it helps me, because before the competition I had all the support from my mum - she's amazing - but she couldn't come. And I couldn't bring my coach either, because that would have been another $5000. I think it's good that I can manage on my own.
''I just wanted to go and make New Zealand proud.''