Autism is hard to explain..........im 17 years old and i still dont get. You find it hard to express your feelings and communicate with others. Also there is always the "something doesnt seem right here"
People with autism tend to be very brilliant at certain things such as maths, but find it hard to do simply things, like answer the phone.
I have found through my experince, that as long as you love and care for that person, that is the best thing you can do. Also when i was young my mother introduced me to new diet which helped me with my autism and escape from my little world. I think you should try that on your grandaughter it might improve her conditon, i mean it helped me.
Cheers!