Here's the marriage details for Ellen Balfe (same for Michael Kenna, so a match):

Ireland, Civil Registration Marriages Index, 1845-1958
Name: Ellen Balfe
Date of Registration: Oct-Nov-Dec 1896
Registration district: Celbridge
Volume: 2
Page: 426
FHL Film Number: 101258

You can purchase this cert from www.groireland.ie if you're interested in ascertaining the name of Ellen's father. I think the cert will tell you the name of the Church they were married in, and if you then contact that Church, there's a good chance they will have the name of Ellen's mother (same for Michael Kenna, obviously!).

On ancestry.com there are lots of other Balfe marriages in Kildare - perhaps siblings of Ellen's??

Good luck.