Hello Karen,
How lovely to hear that you have an interest in finding the birthplace of your great great grandmother, Catherine!
There is a civil parish called
Clongeen, County Wexford so it may be possible that she is from one of the townlands in the area or Clongeen itself. This may broaden your search for church/parish records which is where you will need to look.
County Wexford archives may be a place to start looking if you haven't tried there already. They have some information on records but as I mentioned, you will be looking for church records as it is before 1864 when civil registration was introduced.
The
Family Search website also gives some resource details for County Wexford as well.
A quick check on the
John Grenham website for the surname Miskell, suggests that the west side of the country is most likely for this surname although not a popular name as you say. Foley is a little more popular, please have a look at the page for
Foley in County Wexford for some ideas as to the places again to look. It does show Clongeen as a location for 3 entries.
What records have you managed to find so far that points to Clongeen?