There is a remote possibility that the 1850 marriage of John McDonnell and Catherine Kevane that I gave you is one and the same for 1838. The 1850 marriage does have (assumed) after the marriage date indicating that it could be earlier. The marriage was in the Ballyferriter Parish as stated.
Backing up to 1838 and you most likely have this birth but a Catherine McDonnell was born/baptised on Dec. 2, 1838 in the townland of Ballynagaul which is in the Ballyferriter Parish. The parents were John and Catherine Kevane and the Sponsors were John and Catherine McDonnell. I don't believe the sponsors are the parents but they might be the Grandparents.