Thanks Jim for replying. We have since checked the IGI and found only one listing for Fenagh, County Carlow - Ann Letitia Jenkinson - born 1846.
My young lady would have been approx. 10 years old at this time. She came to Victoria, Australia in 1856. However there were a few Letitia Jenkinson's listed as Carlow (with no town/village name) but none of their parents matched ours (Mother's name - Ann Mathers) so I'm hoping for a response from someone/anyone in Ireland who might be able to help.