Dear Maria
Welcome to Ireland Reaching Out!
Records for the corresponding Roman Catholic Parish of Clontibret begin in 1861. As this is the case, there are some places where you can search online for records of Anna and her siblings. However these websites do not have complete collections and many do not cover the period after 1900:
www.familysearch.org has a huge database of genealogical records including some church records for Ireland.
www.rootsireland.ie have a large collection of Irish Church records, however you have to pay to use this site.
There are 38 O?Connor entries on the 1901 Census in Co. Monaghan:
http://www.census.nationalarchives.ie/search/results.jsp?census_year=1901&surname=O%27Connor&exact=&firstname=&county=Monaghan&townland=&ded=&age=&sex=&relationToHead=&religion=&education=&occupation=&marriageStatus=&marriageYears=&childrenBorn=&childrenLiving=&birthplace=&language=&deafdumb=&search=Search&sort=&pageSize=50
Other important sources include the Tithe Applotment Books and Griffith?s Valuation. Even though these sources only record the head of the household, the information is very important and can be valuable:
Tithe Applotment Books (1823-1837): http://titheapplotmentbooks.nationalarchives.ie/search/tab/index.jsp
Griffith?s Valuation (1847-1864): http://www.askaboutireland.ie/griffith-valuation/
Remember to post any new information that you find here. The more information you post, the more likely it is that one of our volunteers will be able to advise or assist you. Also include information concerning which sources you may have already used so others may further your search.
Best of luck with your search
Clare Doyle
Genealogy Support