This is my first attempt...

Both the births of Martha & her father are well before the start of statutory birth registration in Ireland (1864), so you won?t get birth certificates for them. You might find their baptisms but to do that you will need to know their exact religious denomination and have some idea of whereabouts in Antrim they were born. Otherwise it?s a needle in a haystack. (Co Antrim has 79 parishes, so that?s a massive number of church records to go through without some way of narrowing the search).

Not all parishes have records that go back to the 1700s. Many have been lost or were never kept in the first place. Most censuses prior to 1901 have been destroyed so that source is not generally available in Ireland.

The usual advice in this situation is to exhaust all overseas sources in the hope of finding a reference that helps. Usual sources are censuses, will, obituaries, gravestones, military and naturalisation records.

PRONI (the Public Record Office) in Belfast hold copies of most of the surviving church records for the 6 counties in Northern Ireland as well as some adjacent ones eg Donegal, Cavan and Monaghan, but in order to make effective use of these you will need to try and find a specific parish or area to focus on. The church records themselves are mostly not on-line and a personal visit is required to go through them.

It would need more research, but the chap at this link:

http://www.derek-beattie.comxa.com/family-mc-clure.htm

lists a Margaret McClure of Ballyskeagh. Now Ballyseagh has perhaps been assumed as her birth place, as it seems to have been that of her husband. This Margaret seems to be the same Margaret as listed:

https://familysearch.org/pal:/MM9.2.1/S1WB-XCC

so looks to have been a sister to Martha.

Obvioulsy, a submitted genealogy has to be taken with a pinch of salt and cross checked, but at least if not Ballyskeagh, perhaps she was from that general area. There is mention of other possible siblings at familysearch too.