My own feelings are that a woman takes on that role of matronly habits typically after her first child or after the first child she cares for. Some girls caring for a younger sibling show the tendency too but lose it while women beyond 30 often cling stubbornly to the role if and when they adopt it. Some of the features are nerve wrecking and since matronly also seems to mean to exaggerate it's alienating all the other women away often. From the point of view of the others around matronly often takes on a slight slur or even an insult. That might come from the exaggerated habit of exposing motherly demands and orders by a matron who is encroaching. Also when this happens at a very young age it takes on funny aspects since there are obvious differences between the level of experience and the stance which make the attempt of matronly features especially awkward.