I am the first to admit that I know very little about ASD or indeed many other forms of SN (but I'm learning a lot from reading on here) but I think it is important to remember that AFAIK a lot of syndromes, disorders, conditions have a name because at some point some doctor looked at a whole load of people with a bunch of similar problems and decided to group them together and give them a name. That is certainly the case for my dd and Aicardi Syndrome. There are certain things that typify the condition e.g absent or very thin corpus collosum, infantile spasms, lacunae on the retina but beyond that there are a whole host of other things which may or may not affect them, and in varying degrees of severity.
Not sure where I am going with this... just that I think it is important to remember that each child is unique, and they may have enough things in common with a group of children to give them a diagnostic label or they may not but that doesn't change their 'needs'.
I know in some ways this is easy for me to say because I do have a diagnosis for my dd. But the other thing BH is this - the label I have for my daughter gives me no more indication of what to expect than if I didn't. I think that is what you mean when you say it is easier if it is clear cut i.e you know what to expect so can prepare for it. My dd's diagnosis is as clear cut as anything but I still have no idea what the future holds. Because Aicardi's is a spectrum disorder and all the girls vary enormously, and I mean enormously, and range from girls who only live a few months to those who are able to walk, talk and have relatively 'normal' lives.
Still not sure exactly what I am saying but I think I'm trying to say I don't think a diagnosis will give you what you need. I'm reading between the lines a bit here but I think what you are thinking is this: you want your dd to be happy, you are worried about an ASD diagnosis because you are scared that means your dd will never be 'normal' and therefore somehow never happy, you are desperately hoping that she has a more straightforward language disorder because that means she has a greater chance of becoming 'normal' and therefore have a greater chance of leading a happy 'normal' life. However you see things about her which you don't think are 'normal' and therefore you can't get the possibility of autism out of your head.
Please forgive me if I am completely misinterpreting here and please do tell me to bugger off if I am overstepping the mark but I don't think it is autism you are scared of, it is that your dd will not be/is not 'normal'. That is a whole other issue and one you probably need help with coming to terms with, but it really has nothing to do with a diagnosis for your dd.
I think in a very long winded way round I've just kind of repeated some of what jimjams and davros were saying - sorry, I wasn't even sure where the post was going when I started it!
Sorry too if I am sounding harsh - I do understand where you are coming from and I do sympathise .