The date of birth on a death cert is only as accurate as the informant stated some disagree in one way or another from the actual birth cert, be it a year, month, or day out or all 3.
IrishGen and GRONI are from 2 different sources, the former the quarterly copies, the latter the original ledgers, whilst there could be transcription indexing errors on either, the chances of both doing so are slim and there is no birth for an Elizabeth McKeown on 19 June 1919 in N.I.
If you need a paper certificate you can get it from either GRONI or the Irish GRO for a birth in 1919. The old quarterly indexes (Findmypast, Ancestry, Familysearch) are no use to GRONI, they do not have any pre-partition quarterly BMD copies.
They are largely obsolete for ordering from GROI, Roscommon too.
https://www.irishgenealogy.ie/view/?record_id=5fc6443d7a-445335 or see FAQ on IrishGen
You don't need mother's maiden surname at all for a cert, if tick the box on the search index. If you use the "Order a birth certificate" that has extra questions as most are ordering a recent cert for someone living.
https://www.rootschat.com/forum/index.php?topic=849427.msg7168488#msg7168488No relationship to deceased is legally needed either on GRONI or GRO England to get a paper cert, can just enter none in the box and are presented with a payment page £15 for the paper cert.
Edit: have suggested an index amendment to mother Canning to GRONI.
