My wife is an Early Years Speech and Language therapist, so she is regularly exposed to children with autism.
Your daughter is lucky to have a proactive parent. Even when cases are identified within the system, by nursery staff for example, it seems to be more common than not that parents become very defensive about the idea of seeking further help. And actually, as a parent, I can understand it - but having seen first hand the difference professional help can make, especially in those early years, I would do everything in my power to get expert advice.
In the UK we have the NHS, and even though the waiting lists can be long (because these are the areas that tend to be the first to go during budget cuts), help is freely available. And it's not just autism we're talking about. There could be all manner of things that can contribute to a delay in those early years. There are people who can literally make the world of difference to the rest of child's future, and they really want to help.