Don't worry la...Every baby is unique and there is no absolute formula in their development.
Have you provide an environment for her to learning 爬 (e.g. certain area for moving around instead of holding her all day) or do you help to stimulate her wish to 爬? You can put something that she likes with a distance in front of her, and stimulate her to 爬 and so get the thing. Try it, it should work provide that you baby is not too lazy he he, cause my baby is a bit lazy. She would definitely try to 爬 and get her target. But it is too far, she would rather search for other things to play which near her instead.