Hi Mandy,
Some of my hubbie's family originated from nearby in Gortnagrelly and in Corglass. As the areas you mentioned are quite close to the Sligo borders it can make things very tricky to work out.
It is quite sparesly populated there and very beautiful, BUT going by the census there are a LOT of Rooney's in the area (and still are going by forums on other sites).
I think without more definite info on Annie, you might be chasing the proverbial needle in a haystack.
Do you have her son's birth cert - to be positive that she wasn't married, it MIGHT be possible that she married another branch of Rooney's.
Tara