I have a lil experience with the W going to "global thermo-nuclear meltdown firing 'weapons hot'" department over things that can and should be handled civilly.
My suggestions are first, Focus on your feelings when she does this. Identify that the feelings you sense are your instincts and a lifetime of habitual reactions to such a thing. This is important because as you identify your internal instinct, then you can take the steps to control your reactions. Second, Come up with a short list of statements and ways to react calmly and maturely so that you know what you will do when she goes thermal nuclear. Be sure some of the reactions you will have are general and can apply to almost any blow up. This is important because you will be caught off guard on occasion in ways you never could even have imagined. Third Remain calm no matter what your reaction is. Even if you stumble , if you do so calmly you will be better for it. And finally, you will remove yourself from the situation until she can conduct herself in a calm mature manner.
Your reaction in your post is a good one. Similar to one I have used several times. She will start to get it, even if it enfuriates her at first.
I hope this helps. The fury of a scorned woman is a scary thing for a LBH. But in time you will gain confidence with taking this approach. I have and now the explosions are getting smaller and further away, because she knows I will not stand and listen to it, nor does she get anything out of it. Basically like a child throwing a tantrum. State the boundary, walk away, let it run its course and then rinse and repeat.
Good luck brother. You are taking the right approach IMHO.
Me 46 Former W 46 D19 D7 BD Feb 2016 WAW moves out 4/16/16 D final 6/1/2017
It's time for me to start changin' the way I look at the world......and at myself. ~James Howlett aka Wolverine