Picky kitty only allows certain people to touch her...

My kitty is not one to jump into a stranger's lap. In fact she is nasty to most other people. I warn them not to touch her, and if they try she avoids their hand/smacks them. But some people shes never met before... after about 5 min that they are around her, she will stretch, mew, etc (all the cute things she does) and then let them pat her!! And my mom cant even touch her without a smack! I dont get it. Could it be that I adopted her a bit early(7 weeks) and this behavior is a result of that?

Maybe. But it could also be she likes certain things about people and the people she likes have these qualities.
My cats take to some people and not to others. Sometimes I don't have a clue why that is.

Well, try petting her when she wants to be petted and not the other way around.

With me, she rarely doesnt want to get petted, and when she shows those behaviors I leave her alone. I always tell others that she likes to be talked to, but to not touch her. And then occasionally they pass her "test" and they get to pat her