Should I have told off my "senior" aunt?

This 70 something woman who happens to be my aunt is going around slandering my name calling me a drunk, so I sent her a email and told her off (didn't cuss) -- just basically told her not to call me something that I'm not. She sent me an email back demanding that I apologize to her and that I'm the ONLY disrespectful niece she has and that she is going to call my mother and read her emails I sent her. I'm not apologizing -- I'm in my 50's.