Citizenship through descent

Hello, I have been trying to understand the rules for citizenship eligibility based on descent and it's not quite clear to me.

My mother was born in Northern Ireland but she has British citizenship and has never tried to get an Irish passport or register with the foreign births register.

Would I be entitled to Irish citizenship if I register on the foreign births register? I am certain mother is eligible for Irish citizenship however I am not sure if I am.


I was looking at the table on this website. I think my mother is A which would make me B.
http://www.inis.gov.ie/en/inis/pages/wp11000024

If at the time of your birth, your mother held a British citizenship, you are definitely an Irish citizen by birth and could apply for a passport.