Looking for any family of Margaret/Marjory Hall born 10/10/1886, descended from County Longford

I'm hoping someone can help me.  My maternal grandmother's birthdate 10/10/1886, shown on the 1939 England and Wales register, I cannot find anywhere on the Irish records.  States on second marriage certificate that her father was called Edward Hall, a farmer but no address.She had a child Ernest Scully in Dublin 1914 and then appears on Dublin workhouse register in 1915, with the child, as a single protestant. No records before this.  Cannot find a marriage between the father also named Ernest Scully.  She is then living in England on the 1921 census in Croydon as a visitor, Ernest is in a military school in Harrow, I'm assuming connected to workhouse.  He is killed at the end of the 2nd war war overseas.  My mom was never told of his exhistance.  I've had my DNA done on Ancestry and my mom's birth father was living 20 mins walk from the address shown, a married man with eight children. Her ncestors link back to a couple in County Longford John Ryan and Mary Geraghty.  I've researched most of their children and have no idea who Margaret was related to.  A very complicate and sad tale.  Any advice would be greatfully appreciated.