I explicitly do not want to make a statement about the normality of the described behaviour, as it is impossible to do something like that on a third-person account, even if you were a "professional". And I would like to point out that you are doing the same.

What I criticize indeed is the simplistic view of mental disorders put forward in this article, especially personality disorders. Differential diagnosis is very difficult in psychology as many disorders are disruptions of similar underlying cognitive processes, and comorbidities are common. Their view of schizoid personality disorder is not accurate. For example the part where the author dismissed the psychologist who reminded them that those disorders are only diagnosed in adults. This is what struck me as very odd, which is why I mentioned the age of the daughter. This shows a severe deficiency of knowledge what personality disorders actually are. While there is genetic disposition for developing a PD, they are generally considered to be acquired during childhood and adolescent personality development. In addition, the author seems to get confused by the similarity in name of schizoid PD and schizophrenia (confusingly even though they seem to be aware that the illnesses are different) by assuming a prospensity to having a psychotic world-view.

An outdated view considered it actually to be impossible to get rid of a manifested PD in adulthood, while modern views fortunately see more neuroplasticity in adults. Diagnosing a PD in early adolescence does not make sense, rather one would identify stressors in the environment nurturing dysfunctional patterns and try to resolve those before the behavioural patterns are embedded too deeply.

But it is difficult to tell what the author actually means, as they are somewhat contradictory in their thoughts and seem generally ill-informed about basics.