The answer is
-15See the attached image for the steps on how I got that answer.
Answer: The girl herself ran faster than her friend.
Step-by-step explanation:
This answer, of course assumes a lot of variables, but for the sake of keeping things simple, lets assume the following, the people are ran in a "straight line" with no "obstacles" in their way, and ran on the same track.
Calculating in meters-per-second for the girl who ran 200 meters in 28 seconds, you get 7.14285714286 meters per second
Calculating in meters-per-second for the girl who ran 400 meters in 60 seconds, you get 6.66666666667 meters per second
Comparing the two results, it can be "accurately" concluded that the girl herself ran faster than her friend under the following assumptions earlier stated.
