Well that explains it, she is probably a product of a kitty mill. They generally don't care that a kitten should ideally stay with mom till she is 12 weeks old. That way she has all the manners she needs and will have been exposed to humans at a very young age. Chances are, your kitty was not exposed to humans in the time frame that kittens need to be in order to interact well. If she is hiding, let her hide, don't dive in after her and pull her out, just leave her be. Let her adjust to this new situation- if you could find a littermate of hers, and adopt the littermate that would be good, but again she was probably factorized (mass produced) to sell to pet stores, and when that happens a lot of times the littermates get split up to different stores.
Try interactive toys with her, get an old fishing pole, tie a feather toy to the end of the line and go trolling for her, just drag the line around the bed, or dresser or wherever she is hiding.
Sit with her quietly, in the room she is hiding in. Sit down on the floor sprinkle treats nearby- my cats and kittens love the new treats by Purnina called Aquari-Yums- or look into Kitty Kaviar or wildside salmon- all kitty treats. Then just read out loud to your kitty softly. Do this about 10 minutes a day, if kitty comes out keep reading don't make any moves, don't stare at the kitty, just keep reading. When 10 minutes is done, get up and leave.
Invest in a snugglekittie, you can find them in our Cat Shop section under For Kittens only
And just give the kitten time, it has a lot of adjustments to make, it is stressed, scared, wants mom and its littermates-
also please look at this website and use the ideas inside, like the sock heater, and the alarm clock and start feeding the kitten kitten glopwww.kitten-rescue.com
Good luck- please ask any questions about your kitten here. Lots of people will help you-