I totally understand everything you say about how your daughter reacted. I can safely say I have some bit of autism...all of my friends have told me I have "very high functioning" ASD(autism spectrum disorder).
The best way I can try to explain this is...think of social engagement for people with autism/ASD as an Extremely uncomfortable activity in prolonged doses. Even engaging myself as much as I tried to back in high school and even before, I found I never could fully "connect" with anyone, at least not on that level that I was always capable of perceiving "normal" folks engaging in...talk about a mind killer. That in itself causes PTSD
I can't speak for everyone, but what has helped for me personally is a combination of medical bud, active therapy, Getting Out regularly and exercising, finding and removing all bad influences/bad environments, and kicking my meds.
I mean, make no mistake, I'll always be "different" from those who Don't have ASD, but hey, I feel So much better now inside and out.
I hope everything is going well for you and your family too =) Especially her

It is because eye contact isn't important to us. It doesn't really enter into our minds to use it. I can't really remember what it was like when I was younger but I would never make eye contact and I would refuse to do something if people were trying to make me. There isn't really another connection shared between an autistic person and another person. At least it doesn't occur naturally. It has to be worked on.
Ask yourself why you make eye contact? I will take a guess that it makes you feel closer to a person. I know from a lot of reading that eye contact can make the area of the brain used for socialising light up, but this is non-existent in autistic people.
By the age of 10 I only made eye contact when someone yelled at me to look them in the eye. All I saw was a very angry person and I see that look every time I look someone in the eye.