Great response to your mom. I just hope that this disagreement is not one that is going to be damaging to your relationship with her.
As far as her not wanting to talk about it any more, I feel that way about my adult daughter, who has the same viewpoints as your mom. I just don't want to hear anything more that she has to say about it, because what's the use of arguing? She's not going to change her opinion, nor am I.
Funny - I only have two children - the liberal older daughter, and the younger daughter, a proud military wife who fully supports our President and this effort.
Something to keep in mind when calculating your will.
My sisters are that way --- although they are more on the fence. They tend to be conservative but they balk at the idea of using force for anything except direct self-defense... It's hard to get them to talk about any of it. I don't usually bring it up on purpose or force a discussion, but I don't refrain from offering my opinion on the rare occasion when they do bring up a controversial issue. I'm the baby of the family though and they still tend to look at me as if I don't know or understand anything.