Morbo, I am hardly a seasoned veteran but you have got to set some limits for yourself. You are engaging her in her own games. You have to remove yourself from the conversation. You can still get the last word by saying "I'm not doing this right now" or something non vindictive. And them hang up. And don't answer.
The act is more powerful than the words. The only words that will have any effect are the words that hurt your WW, and those are what she will cling to.
If that's what it's come to and you can only try to hurt her when you communicate, then reevaluate why you're doing this at all.
DB is not about revenge, that gets you nowhere fast.
Save yourself. Nobody is coming! BD:11/2017 Filed:12/2017 Final: 2/2018