How about her son was never on the spectrum to begin with?
I always do the near fatal eye roll reading things like this.
What parents don't understand is a non verbal child can learn to be vocal. Or learn better coping skills. Just because a child can talk and be main streamed in public schools doesn't mean autism disappeared. It means the therapies worked.
Also, there are other childhood mental illness that can sort of mimic ASD. A good clinician can pick a part is this RAD, FAS, ODD, Bipolar disorder, selective mutism, OCD, GAD, SocAD, or crap parenting. Sometimes you get a lazy clinician, and an ASD diagnosis will give you access to every therapy you might need. Also kids grow up and mature.
How much is wrong diagnosis from the get go or maturity and therapies actually working. *shrug*
There will be always two camps. Parents who want a cure, and make this "thing" go away, and others who don't consider it the kiss of deathn and can be successfully lived with at the minimum. Many parents are never in the second camp.