She was a judge, not the organiser, as far as I can tell, although it's great she was able to help, contingency planning is something more for the event organiser. The contingency planning seemed to have been MTGMelee, with untested further contingency options of Challonge and YuGiOh!, all of which failed.

You were able to find one that looks like the format she needed, but what would you have done if it doesn't? Or if it's broken?

It takes time to review > 300 lines of code, and she was on the clock. Even if she is able to read 1 line per second, it would take her five minutes just to read through the code, without downloading it, running it, testing it.

I absolutely agree that there should be a review of the contingency planning, but having more confidence in your coding abilities than your ability to search Github effectively is not necessarily wrong.