What is SO off about a girl losing 10 pounds and running a lot faster?
Anna Pierce in 2008, 2009 was leaner than she is now. Morgan Uceny has gotten progressively leaner since 2005. As previously mentioned, increasing mileage can yield great improvements.
I watched Natasha Fraser run about a 63 to 65 seconds for her last 400 at the 2010 Canadian Championships, almost beating 15:20 5000m runner Meghan Wirght (Metcalfe) in the process. It was a slower paced race, in the 16:40s but still an impressive effort for someone with a best of 16:12.
I would suggest that in the past she just didn't have the engine to match the wheels.