Questions about social interaction of a 6 month old

I was wondering if anyone could give insight on this.  I have a 6 month old daughter.  She is reaching her milestones such as crawling at 6 months, sitting up on her own, rolling over etc.  However, as far as social development she seems to be behind.  When I take her out the house everyone smiles and tries to play with her and she gives little response.  Even when I try to get her to reach out or come to me she doesn't.  When certain family members smile/try to play with her she will scream for dear life as if they are hurting her.  Could this be a sign of a delay?  I would like to know if there is anything I can do to help her develop and be more sociable.

[LRM1021]

6 months is an age when children begin to become attached to a primary caregiver and can get scared when others try to touch them.
She could also just be a serious-type baby-- one who is not very expressive. As long as she is not uncomfortable with you holding her, cuddling her, and seems to be responding to you, I would not worry. Your pediatrician will also check for responses regularly at check ups. If you have concerns, you could mention it -- but 6 months is really too young to be worried about this kind of thing.