If she is 14 now (but about to turn 15 soon) then she could be a soph who is young for her grade.
However, based on what you have told us she was in 8th grade at the time. If you are 14 during summer (when she ran the race) then she is a freshman now.
A 5:02 is right up there with the best ever if it was done in 8th grade. The tough part is continuing to improve to 4:55, 4:50, 4:45 through until senior years.
If you look at the results of FootLocker over years, you will see that the girls race is won by 9th, 10th and 11th graders MUCH more often than the boys race. The boys winner is nearly ALWAYS a senior.
So, while a HS boy may run 5:00 in 9th and improve to 4:40, 4:30 and 4:20 by senior year, a HS girl is much more likely to stagnate or regress to being slower than that 5:02.
Also, I have never heard of a "North American Championship" for track or XC for 8th graders -- unless you mean the Hershey Track and ...
oh wait, I found it. It is called the "North American Finals" ... I didn't realize they included Canada. My teammate ran in those as an 8th-grader. He ran 4:24 in the 1500m for second.
Here is the result, it would not have taken too much to find this:
Event 5 Girls 13-14 1600 Meter Run
Record: 5:01.24 R 2007 Claudia Francis, Queens, NY
Name Age Team Finals
1 Phelan, Jaimie 14 Kitchener, ON 5:02.95
2 Forsey, Jillian 14 Kippens, NL 5:08.70
3 Kendall, Kali 14 Brooklyn, NY 5:09.84
4 Hawkins, Amber 14 Maudertown, VA 5:10.17
5 Brown, Maddie 14 Tulsa, OK 5:22.12
6 Zarate, Yajaira 13 Lynwood, CA 5:34.98
7 Brown, Cassidy 14 Auburn, WA 5:41.43
8 Burr, Jackie 13 Westerly, RI 5:42.27
9 Koshinsky, Beth 13 Jensen, SK 5:43.03
Not sure if Canadians have five years of "high school" or whether they start theirs at age 15, but either way this girl is WAY AHEAD of most everyone her age in the US or Canada.
It would have taken me A LOT of training to be that fast at age 14. I was faster by age 15 (I am male) but that is FAST for a 14 yo girl.