My girl is behind 😞

My almost 16 month old isn’t saying words. She babbles all the time though. She understands a lot. I work with her all the time but she just isnt interested in anything. I think she might be autistic. Nothing wrong with that. I mentioned it to her pediatrician and he just looked at me like I was crazy. She shows a lot of the signs but might just be cause of her age. I just want to help her. My sister in law tries to brag about her 9 month old, how he can say all these words. Makes me feel like crap. My daughter isn’t around many people besides me and her dad. Could this be the reason? Her pediatrician is setting up an appointment with a neurologist if she hasn’t learned words by 18 month checkup. I just feel like I’m failing at everything 😞