Crawling is very important to the brain and cognitive development of your baby. It facilitates the left and right side of the brain working together. Not only does it strengthen their body, it also gives them important EXPERIENCES they need for development. Encourage your baby to crawl by getting down and imitating crawling. You can also do cross-patterning with her: lay her in front of you, touch her left hand to right feet and right hand to left feet. Repeat. You are moving opposite limbs at the same time, which is what happens in crawling. Your baby is also more likely to crawl if you let her spend most of her day on the floor (not confined in a stroller, car seat, swing, etc) and if you do not put her in a sitting and/or standing position before she does it by herself. Read more about it here.