Questions about Pomeranian behavior?

I have a 4 month old female Pomeranian, my first one. I also have a 3 1/2 month male dachshund. I'm beginning to notice more and more that my dachshund alvin loves people, loves to lay with you, comes up to anyone wagging his tail happy as can be. My pom on the other hand is kind of distant. She either barks at people or she runs off when they approach her. Often times she runs off from me when I try to just pick her up! She's just not as people oriented at times. Other times she runs under my feet to get away from Alvin. Also if she is only about 2 1/2 pounds at 4 months old how big do you think she will get? I met her mom and her mom was very sweet, you think she will grow out of this? Anyone ever experience this type of behavior in a pom?? Any advice is appreciated!