Denial. "No, she's fine. My kids do all that too." Which just makes you feel lame, like you're overreacting and inventing the difficulties of raising this child.
Blame. There will be discussion in some circles on how you may have caused it. The ones I got were that I must not have talked to her enough as a baby, and that I was too uptight and hovering when she was a baby.
Congratulations on your diagnosis! Support is nice, though it's not quite like winning the lottery.
The reaction you want, and SHOULD get if this were a perfect world:
That's so great you are getting help for her! You are doing a great job! Let me know how I can learn more about autism.