Could this be Agnes ? Well I suppose it could but it is a bit strange to just have the title Mrs and no Christian name on a records. I don't think I've ever seen that before.
The death for Phelim/Phelan/Pharlan in 1872 would, along with the other possibilities found by you good folk,  give a time frame of 
Phelim McPartlan birth 1788, 
baptism of Phelim  McPartlan and Kitty Dolan's  son - Stephen McPartlan 1837 
remarriage of Phelim to Agnes 
birth of Phelim McPartlan and Agnes Neillan's daughter - Mary in 1847 ( from her marriage certificate in 1871) 
marriage of Phelim McPartlan & ?? son Michael McPartlan, a widower, in  1867 
All of which, on paper, looks as though it could work. I've now recorded on my paper records  but wont be adding it to any on-line tree as I don't think its enough enough to confirm that they are all the people from the same family. I would love it if it was!! Would you agree or am I being just too cautious? 
I've seen to many warnings on here about people who add names that are possibilities and before you know it they have a tree that is full of just that ... possibilities. 
A big thank you to all who have pondered over this, made suggestions, searched for things and posted.