Flahy

[Michala]

Think it could be new Ross Wexford

[Michala]

This was Margaret in the 1851 cencus

[Wexflyer]

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.

[Wexflyer]

Think it could be New Ross Wexford

Yes