Prolly too late to jump in here but...
Rio Carbon 5GB
They are solid stuff with better electronics than the ipod mini. It also holds a bit more for the same price (about $200USD).
Problem is you almost never see them in stores
Btw, if it's just for cardio she'd be better off with something solid state (i.e. not a hard drive player); because you can kill hdd players with alot of bouncing, running etc. Depending on how her files are encoded you could definitely fit 50 songs on a 512MB flash player. The quality of the audio will go down (because of the components used) but with shitty headphones/ear plugs it doesnt matter much anyway.