on the irishroots website, there is one Mary 'Murren' with mothers name Scanlon born in Co Sligo in 1843.
It would cost 5euros to access the full entry and find out the parish - I think for a small fee of around 40 dollars or so and with a bit of time and luck you may find who you're looking for.
However, there are records missing and some parishes not covered - it would be useful to contact the County Sligo Genealogical Centre and ask them where are the missing records if they do in fact exist.
I may have a chance to go to the National Library to do some research of my own and if you had an idea of parish and year I would be happy to look something up for you. However, I don't know if I will have a free morning before say Christmas.
Another new source is the Tithe Applotment books which are now free online through the National Archives of Ireland website.