My baby was like that too - even when she was only 2 months old! I think some babies just know the feel and smell of their mom and they like to stay put. Maybe they're smarter than the rest!  My baby stayed like that till she was about 2 years old but then she became much more social. Babies are just small people with their own personalities so I guess some of them just want Mom.

If you let other people hold her instead of taking her back, maybe she'll get used to someone else's arms. I had to go back to work when my infant was 6 weeks old. He got used to the caretakers at his daycare - he had no choice. He became "social" whether he wanted to or not. I think you shouldn't shelter your baby so much - give her a chance to learn about other people and she'll find it easier to be comfortable with them.

I had to go back to work when my baby was 1 year old. He had separation issues till he turned 3 even though he was exposed to lots of people. I think the child's nature has a lot to do with it. Some kids are clingy and like to be with Mom whereas some are really curious and want to get out there.