Hi, thank you so much for your help, I guessed as much.
My friend has found her paperwork and she says that she has an invoice from William Whelan Funeral Furnishers of Grey Abbey, Kildare dated 28 Feb 1946 for the funeral of the late Patrick Maher dated 26 Feb 1946 and a telegram to one of his sons saying 'your dad died today 26 Feb signed Matron' So I think we can conclude that Patrick got his wish and was buried with daughter Catherine (Katie) in Grey Abbey and so was his wife Bridget, as you found.
Apparently, there was a metal cross grave marker which I expect has gone by now.
Strange that we can't find a death record, but never mind I think we have enough to go on. I don't have any experience in finding a plot number in Ireland, in England I would email the local council do I do the same in Ireland? Can you help me in this?