Veronica,
Could this be Marianne's (Mary Anne) family in the 1901 census at house 2 in Treanmanagh? (see attachment)
They seemed to have vanished from that townland in 1911 as they are not in the census there. Too bad because that census indicates how many children a woman gave birth to, and how many are still living. She could be the eldest child in this family. I did not locate a birth record for her which would be helpful because normally a couple married in the wife's home parish, and if the RC Miltown Malbay marriage record of 1895 is correct, she should be from that parish. If she is from the RC parish of Kilmurry Ibracken which is where Treanmanagh is located, then one might find her birth record there. I looked on the Clare Library site in both parishes, but did not see her record. No record found on irishgenealogy.ie either.
Finally, regarding James O'Connor...on the Clare library site there are three sibling records in Miltown Malbay with parents James O'Connor & Catherine (Kate) McKnight:
20 Jul 1859 Michael
22 Jan 1864 James
24 Jan 1872 Patrick - on his record, the townland shows Kil(?)....possibly Kildeema as it shows in James' marriage record....just a hypothesis.
Also, the 1901 census for James and his family, it shows Kate O'Connor, mother living with them. This 1864 birth date is pretty close to agree with other records. Again, I don't know why James and Patrick do not show up in a search on irishgenealogy.ie.
Regards,