Oh, heavens Isinde, that is hard, I didn't know.
My family are / were all mad, rosary-bashing, mass-going, pope-loving, Irish rebel song singing, 2nd generation immigrant Irish Catholics (hence the drink issues I guess) but some more tolerant than others.
My cousin's eldest son is gay, (very close family, they lived a few doors down and we were together all the time, mum's brother's son) and on her deathbed my very Catholic mum asked me if I thought T (her adored first nephew) was gay (he was 16 then, came out the year after). I said we were all fairly sure he was and hoped he would find the confidence to tell his parents soon, and she just said she had thought so, and she just hoped everyone would support him. Because even though she was born in the 1930s and from a fervent Catholic family, she also lived in the 21st Century!
But he (and my cousins) decided not to tell either set of grandparents (one set now dead, one bigoted old grandma still alive) as there was no need for them to know. As we knew they would be arseholes about it (not to mince words). As if a personal issue of his life, that had no more to do with anyone else than if he liked one football team over another, would change the wonderful, caring, clever and funny boy he is.
So I can sort of understand (though not at all really) where you are coming from, as what you went through with your mum is what we sought collectively to protect our T from, but with grandparents. And clearly, your mum is wrong. Very, very wrong.
But sometimes people are the victim of their upbringing and the inherent prejudice that goes with it. I don't know if it is wrong in me (hater of conflict), but I often overlook the politically incorrect comments of older people because I assume they are well-meaning, but victims of being brought up in a time and community where prejudice prevailed, and there was no logical counterpart to challenge it. And sometimes family boundaries can transcend that. I cannot help you deal with the hurt of the past, but I hope and wish that you can find some path to bridge the gap, and I am sure you will find some solace in being with your mum and talking to her soon.
I hope this hasn't been a clumsy, intrusive post. We can never truly understand anybody else's family dynamics (frequently not even our own). Just want you to know I care. About you, and all the babes. xxx