Catherine was probably the daughter of (and first child of) Humphrey Collins (1785 - 1873) and Johanna Barnane (BD dates unknown), baptized 02-Dec-1820. On Catherine's baptism record, I think the father's and godfather's names were transposed.
Another possible wedding witness named Humphrey could have been Catherine's cousin or close relative, Humphrey Collins bap. 01-Aug-1831. Honora could have been Catherine's sister, Honora (Norry), bap. 17-Dec-1829.
The known children of Denis and Catherine were all baptized in Skibbereen R.C. parish. They were:
Julia, bap. 20-Dec-1851. Godparents Daniel Donovan and Honora Collins.
Mary, bap. 05-Dec-1852. Godparents John Donovan and Johanna Collins. Johanna could have been Catherine's younger sister, bap. 07-Dec-1835.
Johanna, bap. 27-Nov-1853. Godparents Daniel Regan, Johanna Cadigan.
Honora, bap. 11-Oct-1855. Godparents Mick Collins, Catherine Collins.
Cornelius, bap. 11-Nov-1859. godparents Dan Donovan, Catherine Bohane.
Ellen, bap. 23-Apr-1864. godparents Daniel Donovan, Margaret Coakley. Coakley is a very Lissane name.
Catherine, bap. 25-Jun-1865. godparents Patrick Regan, Norry Cady (Keady).
Catherine Collins Donovan and her family are entered in Family Search Family Tree (registration is free). Her ID # is LKCD-M3S. Her father, Humphrey Collins is ID # LKC8-BYD and her nuclear Collins family are entered there.