I believe that the family neme you are researching was FAHERTY, not FLAHERTY. THis was confirmed by looking at the 1911 Irish Census.
My Rosmuc data shows Mary being born 03 Nov 1898 in Inver, Rosmuc to John Faherty & Mary Keane. She came to the USA via Philadelphia in 1920 to join her aunt Catherine Keane. In addition, my data also shows that Kate arrived in Philadelphi in 1923 at age 20 to join her sister Mary.
Hope that helps.