Illusive Ellen Chapman my 2x great grandmother- Clara

Ellen Chapman has been a brick wall I and my father's cousin have been trying to break for many years. Here is the information we KNOW.

Ellen has an illegitimate daughter Mary in Kilbride, Clara on 26/4/1871, birth certificate gives the informant as Bridget Geoghegan. Four days later Mary was baptised in Clara Catholic Church with the following information recorded - Bastard Mary, daughter of James Fitzpatrick (reputed father) and Ellen Chapman, sponsor Bridget Geoghegan.

FAMILY LORE  said Ellen Chapman was Protestant so it was hugely serendipitous that I found the baptism record in the Catholic church when I wasn't looking for her. Apparently Ellen had at least one brother who was something to do with the church curate/preacher possibly.

It has also been passed down that Ellen married a dairy farmer and had two boys, they didn't stay in the area but hadn't gone too far away. An uncle who is 93 recalls being told that Ellen and her husband died in 1919 from a buggy accident. They were going along a sandy road when the buggy slipped and fell into a quarry. They are buried in Glasnevin cemetery, but without a surname I'm not sure how to trace that further. I've looked for her in the 1901 and 1911 census, as well as the civil register for marriages to no avail.

Mary married John O'Shea in 1889 in Clara and I was told she was cut off as John was Catholic, but my father's cousin was told it was because John was in the army. Their first born was called Mary Ellen in the hopes it would mend the rift but it didn't. So there is a possibility that Ellen was Mary Ellen.

As you can see, there are lots of things we think we know, but little information for what we actually know. Any information or tips where to look next greatfully received, thank you.