Born 1798 in County Mayo.
http://www.werelate.org/wiki/Person:Mary_Gallespie_%281%29
Newly arrived free passenger Mary Gillespie, who was residing with her uncle and aunt Dominick Gillespie and Mary nee Munnelly.
Hi
Both of those surnames you mention are popular in North Mayo especially the Crossmolina +Ballina + Killala areas. this is a good website for North Mayo
Online searches that are available are (but maybe too late for you)
Tithe Applotments and 1901 and 1911 Census
http://www.genealogy.nationalarchives.ie/
Griffiths Valuations(1850's)...will show you landholders but also will locate the village of origin
http://www.askaboutireland.ie/griffith-valuation/
Hope this helps, good luck with your research