You can't expect her to digest food faster than a few hours...if her food was shooting straight through her, there would be some serious issues.  Sounds like she's fine to me.  If it was taking 3-4 DAYS, then I'd be worried, but not 3-4 hours     
				__________________  ~Magnifique Yorkies~  Purchasing from backyard breeders, pet shops, and puppymills perpetuates the suffering of other dogs. 
Educate yourself and buy from reputable breeders or rescue.      |