demeanor after sickness

Question
I know that you are not a vet, but I was wondering if, in your years of experience working at shelters and seeing sick puppies, have you ever noticed that it takes a while for puppies to get back to their normal behavior.  Four weeks ago, our two 13-week old puppies came down with Parvo.  One is fully recovered and bouncing off the walls, but the other can't seem to get out of her funk.  She is always tired and we can tell that she is not 100% normal because she has spit up food after eating too fast or getting too excited after eating.  So, my question is, is it normal for a puppy to take a long time to recover (she has been home for 3 weeks now)?  Could she be depressed?  We just wanted a second opinion about how dogs recover from sickness, because there is not much information out there and our vet doesn't seem to concerned about it.

Answer
Well it is probably her personality more then anything,puppies that are more quiet and shy tend to take a little longer to get over things then puppies that are hyper

If your vet isn't concerned,I wouldn't be concerned either-her stomach may still be a little weak for a while,in few weeks if it doesn't get any better you can even ask another vet for a second opinion