Hi There,
I am a Pediatric Occupational Therapist. I can tell you that there is great importance to the milestone of crawling. Many kids currently skip crawling because of the lack of Tummy Time, partially because of the "Back to Sleep" Campaign. Because they are not on their belly's as much, they don't develop the muscles in their neck and back as quickly. Crawling also requires and develops bilateral integration, coordination, and visual motor skills. Just because she hasn't crawled yet, doesn't mean that she won't in her own time, but it doesn't hurt to get her evaluated by a Physical Therapist (through Early Intervention). A Physical Therapist or Occupational Therapist may be able to pick up on other reasons why she is not crawling, that are not necessarily just related to muscle strength. No offense to Dr.s, but they only see your child for a few minutes, and not in the context of their daily routine, so it is hard to get an accurate measure of the child's overall development. I am sure she is fine, but even if she does not qualify for services, the therapists may have some ideas to help her develop the muscles and coordination she needs to crawl, which also improves and preceeds other parts of development. Crawling encourages visual motor skills and builds strength and coordination. Whether she does it in her own time or with the help of professionals, please don't overlook the importance of this milestone!