Hi GS,
Another method:
Mother: "Barb.....aggressive antic.....subtle sabotage....blah blah blah etc"
GS: "Well, mother, I must be going now. Gotta go pumice my heals. TTYL. Bye." click. phone off hook.
An exit might not be the ultimate reaction but is useful in that it stops you from responding verbally .....keeps you from taking the hook, so to speak. You can then examine your reaction and think up ways you'd like to respond in future.
Also, totally ignoring the hook by acting deaf and changing the subject:
Mother: "Barb.....aggressive antic.....subtle sabotage....blah blah blah etc"
GS: "You know mother, I was thinking of pumicing my heals. I find it's something I need to do now and then. Do you know where I can find a good pumice stone?"
And see her reaction (

might be entertaining to boot!).
When all else fails:
The......you must be kidding response can work:
Mother: "Barb.....aggressive antic.....subtle sabotage....blah blah blah etc"
GS: "Oh mother! (giggle, choke, spit), you can't be serious! (ha ha ha). You are a riot sometimes!"
Not exactly lovey dovey communication but sort of happy go lucky, light and bubbly stuff and most important it says: "I'm not biting".
Here's an interesting link:
http://www.psytalk.info/articles/narcissist.htmlSela