I seriously don't understand how a 15 year old girl can beat top professional girls in their mid 20's.
In few month she improved her time with more than 10 seconds, it's not possible without doping in my opinion. I have a huge passion for swimming and know how hard it is to improve your personal best. Therefore i seriously doubt Ledecky won fair and square.
Hard work won't do it alone in this case, sorry.
Mod Edit: A reminder to everyone that accusing people of cheating without providing any evidence to support your statement will not be tolerated.