Aww..poor kitty. She must be so uncomfortable with those hard stools. Give her stool softeners until you find out what her issue is when you take her to the vet’s. The KMR is very good, like Savas was explaining. And also a bit of canned pumpkin and physillium husk. Physillium Husk is a bit tricky because you do not want to give her too much as it will make her more constipated; but the right amount will get her going. Ultimately, you could try getting foods with higher fiber content. Hill’s r/d could help her out, or Royal Canin Veterinary Diet Feline High Fiber dry cat food (For Kittens) I don’t usually recommend these diets but you can be successful with them in your cat’s case. Good nutrition is important so, with your vet’s guidance, try to look for high quality foods. Here is a good website on high quality foods. It ends in (.org) so it is reliable.
http://www.catinfo.org/commercialcannedfoods.htm
Hope she gets better. And always consult your vet before doing something drastic. She will be fine with KMR, though. Cats usually love it!
Good Luck!
Try picking up the liquid supplement KMR milk replacer. First, it will give your cat neccessary nutrition that it didn't get from good ol' fashioned mother's milk.
Secondly, liquid milk replacer can have the unfortunate side effect of causing loose stools and diarrhea in cats.
In a case of hard stools, it could be just the trick to "loosen things up". ;-)
Hopefully the situation will resolve in the next week or two. Sometimes kittens develop mega colon, crystals, or other issues that carry into adulthood when taken from their mothers to young. If this is the case, a proper diet/medication regime can alleviate the situation and give kitty a happy, normal life.