It is pretty much impossible to do that for a longer time. Depending on how big the group is that means she is running at least 4 to 5 times the distance the group is doing while moving forward at the same speed as the group is doing therefore also her speed needs to be 4 to 5 times the speed of the group.  Lets assume the group is slow and runs at 6hm/h which is very slow and they are doing a short run of lets say 4 km. And lets say the group is small so the distance to run around them is like a 4 times multiplier. That means fatty runs 16 km with an average speed of 24km/h. That is faster than elite marathoners. That is close to world record. That is totally believable.  This shows that fatties have absolutely no idea of exercising and just lie.