Her father John Barr Johnston (1843 - 1919) was a knight, a merchant, as well as an alderman, mayor and justice of the peace from Tyrone.
Coincidentally, immediately after his death on Friday, 22 January 1904, Johnston became the first woman undergraduate to succeed in registering at TCD, and by the end of year other women had done likewise.
[7] She recalled, "When I arrived in Dublin 1904, I was informed that he [Salmon] had died that day, and the examination had to be put off until after the funeral.
Although "an active and able student" Johnston left before finishing her degree due to ill health and marriage.
[13][14] The family later moved to England where Johnston became a founder member of the London branch of the DU Women graduates association.