RootsChat.Com

My take on all this is as follows:
Margaret Kehoe emigrated to Britain at some point before 1851.
Presumably she got married and had children.
Marriage record will give father's name and profession (if 1835 or later, and married England)
Can you confirm that was checked?
Presumably says James Kehoe - is that correct?
What was his profession?

But that leaves the name of the mother unknown.
At some point, someone in your family decided she was Mary Flahy. Why?
As already pointed out, there were multiple Margaret Kehoes born in and around both New and Old Ross at the time in question.

James kehoe died Nov 1868 • Ballycullane, Tintern, Wexford, Ireland, Margaret the daughter ended up in Falmouth but I have no more info on James kehoe or Mary flahy.

James Kehoe is a common name. Why do you think the chap who died in Ballycullane in 1868 is the same person as the James Kehoe of Old Ross in 1801? Absent some specific link, the chances that they are the same person are very slim.

Trying to find info on Mary flahy, married a James kehoe, she was born about 1780. Any help would be much appreciated.

This is a classic example of an enquiry where you make it very difficult to help you - you provide no context, no detail!
- Why do you think she is connected to Wexford?
- Religion?
- Where did she end up
- What was her station in life?
- Why are you only asking about her, but not her husband?

All of these sort of details help to form a picture of where she might be from.

For what is is worth, your best bet is New Ross, but 1780 is before start of Catholic registers.

Address on the marriage registration for Elizabeth Dooley is hard to read. Looks like Lightwater to me, but there is no townland of that name in Wexford. Any other ideas? Last marriage on the following page
https://civilrecords.irishgenealogy.ie/churchrecords/images/marriage_returns/marriages_1869/11414/8192447.pdf

Ah - I thought there was some change. Why I asked!