Vicki, my son was adopted out of foster care with similiar pre-natal issues. Lucas taught himself to read at two. He is on the autism spectrum, although we couldn't get the diagnosis. until he was eleven. We suspected it so we demanded interventions and he got them. The neuropsychologist who diagnosed him said that substance abuse causes more Autism Spectrum Disorders (ASD) than in kids who were not exposed. Your daughter sounds like she may very well be on the high functioning end of the spectrum. My son had a speech delay too, typical. He wasn't #2 potty trained completely until age four. My son is fine with large motor, but fine motor is still a problem. He has trouble printing, let alone writing, even at age fourteen (almost).
We thought he was a genuis when he learned to read, but, as school progressed, he actually struggled. I'd try to get her in interventions regardless of her current diagnosis. It can do wonders. At her age, I'd see a neuropsychologist.