Roots Ireland has 3 records of children to David Foley and Margaret Hennessy. These are from Rathcormac parish which is in the same general area where the Kirby family lived.
Catherine Nov 18 1833. Address: Redota.
Johanna Jan 31 1842. Redota.
Margaret Oct 3 1845. Address: R. Dothigh (?)
You can view these records on the following link, it might be worth going through the parish registers to see of you could find a baptism of Mary, if this is her family.
Trying to find John Kirby will be a bit more difficult as the name is very common. Roots Ireland has records of 19 John Kirbys born between 1830 and 1840 with a father called John Kirby.