There's this distance runner sophomore girl on my team who had some pretty impressive results this year. She runs very little mileage (20-25 mpw) and has solid natural speed. At the beginning of the season, her mile PR was about 5:25. Then, during the last two weeks of the season, she lowered it to 5:12, then to 5:09. If she actually put in work/mileage, how good could she be??