Just so you know, they can't revoke your membership for something like this and if they did, you would have grounds for a whopper of a lawsuit unless they are willing to ban any and all conversation about any and all possible controvesial subjects and post those rules in writing.
She may not like your way of eating, but she has no right to tell you not to discuss it or answer questions relating to it if asked.

This is just me, but if it were me I'd probably make an effort to bring up the topic every time she was around and then remind her of my "freedom of speech rights" if she got in my face again and possibly even mention the "L" word if the old biddy didn't want to back down.