I have two children; a son who is high functioning on the autism spectrum and a daughter that is what they call "neuro-typical" (no autism). When my son was 18-months, he didn't respond to his name and he wasn't talking, but he also avoided all eye contact as much as possible, didn't appear to understand what we were saying, wouldn't play with anyone, didn't know how to play with any of his toys, had repetitive movements . . . oh dear, the list just goes on and on and on.
As for my daughter, by the time she was 18-months, she had a number of words under her belt and quite the socializer -- definitely not autistic -- but she still wouldn't respond to her name sometimes when I called out to her from across the room. What I learned is that all children have an amazing ability to tune out the world around them and can become hyper-focused on whatever they are playing with or watching on t.v. It is always good idea, when you want to tell them something, to go up to them, get down to their level and tell them what you want to tell them. Never assume that you have their attention or that they can hear you.
As for your daughter, it is good that you are having her evaluated. Maybe she just has a case of selective hearing but possibly she has an issue with her hearing (make sure they test her hearing), a speech delay or maybe some auditory processing issues. If that is the key, then early intervention is the key. Luckily for us, we caught my son's autism with he was just 18-months. He has made an amazing recovery since that time and unless you know something about autism, you may not recognize that he happens to be on the spectrum. You would probably just think that he's the quirky, shy kid.
Anyway, I hope this gives you some valuable information that you can use. I hope everything goes well for you and your daughter.