Hello,
The diagnosis of autism is a medical diagnosis, ie; it done by a doctor, however good practice is that is done by a multidisiplinary team, usually involving a speech & language therapist (SLT), occupational therapist, paediatrician and an educational psychologist (EP). Most areas will have an autism assessment team who would receive referrals from professionals such as SLT, GPs, EPs or health visitors. Often children may not be referred before 2 years 6 months ish.
The diagnosis is based on behaviours so there is no blood test etc, the child would be observed, ideally in a range of settings, home, pre-school and clinic and the parents are asked questions and the child may be asked to complete some tasks.
It might be worth asking your mother in law why she thinks your daughter may have aspergers. Often aspergers is not diagnosed until children are older because the behaviours associated with aspergers are often more subtle than autism and do not always appear until a child is older.
I would go to your GP and speak to them if you are concerned but if you don't have concerns about your daughter then I wouldn't worry.
