"The linked couple" is a strange phrase although I suppose if they were linking arms at the time, they might be described as such.
However, "... the owner was accustomed to speak and be heard" is very unnatural. I cannot see why it wasn't written "... the owner was accustomed to speaking and being heard". Perhaps, at the time of writing, "accustomed" was followed by the infinitive etc but I somehow doubt it.
As far as the meaning goes, it means that her tone of voice showed that she was used to people attentively listening to her whenever she spoke. She was not used to being ignored. The "be heard" part is the relevant part here.