If not Mary Kelly, someone from that village (area) knew a Davies died in a mine accident in 1880 and spoke about it to Joe Barnett. This was local to Wrexham knowledge not national news. Whoever told him that snippet is 'Mary Kelly' and that person is interested in, and is knowledgeable of, the Kelly Family. Maybe someone envious of Mary? Why did she need to recite this after eight years? A rival perhaps? She also knew of an ironworks in Brymbo, again local information.
Maybe this person’s father is called John. Then it’s her brother who’s in the army and his first name is Henry just not followed by Kelly.