I think my kitten might have a behavior problem? Please Help!?

[orangesandlemons]

I adopted my 9 month old female kitten from an animal shelter. I adopted her with her mother. The mother is fine, she shows affection towards us, is inquisitive and leads the life of a somewhat normal cat. But I worry that there is something wrong with the kitten? She is afraid of everything, even at the slightest noise she will run away. She won't let anyone in the family go near her. She hisses at everyone if they go too close to her (but doesn't attack). When she's not hiding, she's sleeping on the other end of the house, under the piano. She only ever leaves that place to eat and use her litter box, and then goes back.

So to brief the important points:
- She has been like this ever since we got her (September 2010 --- she was 4 months old then)
- She runs away when we go near her
- Doesn't like anyone touching her
- only ever comes out to eat and stuff, then goes into hiding again
- Hisses a lot
- Frightened of EVERYTHING

I am worried that there may be something wrong with her. Please help! What shoulld I do about her?
I have tried the baiting thing, but she not interested in anything except for running away from everyone! I've never seen her do anything but sleep and hiss and run away and things like that. She doesn't play (even when she was younger) and I've never seen her groom herself. I was told that I should increase my contact with her, and I started to try and groom her every day for about 2 weeks, but that just made her even more scared! I've tried everything, and now I don't know what to do about her!