I was just about to say this. In fact, double negatives were commonly used in earlier forms of English to create a more intense negative. Many of our language rules are arbitrary and are not actually followed by native speakers of English. There can be negative consequences for using non-Standard English in certain situations (writing an essay, giving a lecture, going to a job interview, etc.), but generally grammar doesn't matter as long as it can be easily understood.manic_depressive13 said:"I don't know anything" isn't more correct or logical than "I don't know nothing". Someone just decided one day that people shouldn't use double negatives in English. The first thing they hammer home in university linguistics is that you're not better than anyone for obsessively adhering to the rules of standard grammar. You're just limiting yourself and being a classist tool.
And I don't know about correcting adults, but I have read that correcting children rarely causes a change in their speech patterns. (For those who love sources, this was in Language Files: Materials for an Introduction to Language and Linguistics, 11th Edition, pages 314&318.) I imagine that adults are better at consciously changing their speech, but for the most part people seem to unconsciously pick up their speech from whatever they hear around them. OP, if you really want to change your mother's speech it might be better to just speak "correctly" to her as often as possible so that she might pick up the habit as well.