I am currently pursuing my BCBA, and the Verbal Behavior approach addresses this very thing. Begin working with her on requesting things that are reinforcing to her...either verbally or with sign (or PECS if you choose). You want to find out what motivates her to make language meaningful to her. Pointing to a picture is not meaningful right now. Check out Mary Barbera's book The Verbal Behavior Approach: How to teach children with Autism and Related Disorders. Good luck!!