She ended our argument by saying that she'll never condone or accept it. All during this, she was occasionally breaking down in tears; and when she cries, I can't help it, either.
I'll give you twenty-to-one odds that she's being dramatic. Probably not deliberately - but she's upset at the moment. I'm 59, and a grandpa, and I've watched a lot of my kids' friends grow up to do or be things that their parents didn't really have in mind. Nearly all mothers, more so than fathers even, I think, still hold their kids as "my baby first and the rest of the world can go to hell." Never is a long time, and you will still be you, gay, straight, or Scientologist.
And crying is part of it, so go ahead and cry when she does. Just be true to yourself - you are the one that has to live with you
all the time.