Getings ancestor

Hi there, I'm trying to locate records for a Mary Getings/Gettings born around 1804/1807 somewhere in Sligo.
I cannot locate any records for her prior to marrying my 3x Grandfather John Drinkwater in 1840, in Cheshire, England. At this marriage she 
is documented as a Widow and it seems her previous married name was Morrison. She gives her father's name as John Gettings/Getings. She states her place of birth as Sligo, Ireland, but I'm not sure if this is Sligo itself or the county as a whole. I can find no other records pertaining to her prior to 1840.

Do you know how/if I can search records specifically for Sligo? If I can locate her birth I then hopefully can trace further back. I have tried looking at the Irish census but what records I have found don't give anything other than how many of the same last name are living in a house. Is there any way I can find out more details - if there are any? I'm aware that there are numerous possible variations of the last name and that Mary may not be her Christian name but if I could find a female Getings/similar having been born around 1804 in Sligo it would be a start. Following her marriage in 1840 she appears on England Census records until her death, so I assume she left Ireland sometime between birth and 1840.

Apologies for the rambling message, but any possible hints you can give would be much appreciated. Many thanks, Christine