Not sure of what you mean in your first sentence. I certainly was not in the top 100 and never have been. Can't recall if she was that time, but she is frequently in the top 10 within the top 100. I have no idea how she is doing it and am not making any representations in that regard. I do wonder how some people can be so fast. But since there are often 300,000+ players for a challenge, that means 3,000+ groups, so less than 3% of those who finish first in their group will make the top 100.
MJeff1 is not my screen name that is used in Xbox. I can assure you I do play the challenges and have no ulterior motive for posting here.