BR: This little motto helped me with my ex and current wife: "I will not participate in you being pissed off at me." Just let it slide off your back, BR, like water off of an otter's back.
Another thing that helps, but only if you, as an old heathen, can imagine yourself as a bit of a Buddhist. Take in the poison she is sending you as a breath of air, hold it in, letting your body cleanse it, then release the breath, sending it back to her filled with loving kindness.
Geeze, my wife is a Buddhist, I'm Jewish, and I know that the above "meditation" may sound a little weird, but I've tried it and it does tend to work, at least in a subtle way. Of course, if she gets even more pissed off because you're not engaging in the fight, there's always that little advantage. :^)
