Sheesh, sounds like my sister on a good day. I understand ALOT better now
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I zone out most of the time I'm around her. Which thankfully is only on rare family occasions. Zoning out works, unless she insults me, recently I've resorted to retorting and making her feel tiny and then I swiftly move on, allowing her to absorb what just happened (HUGE feat for me, she's 12yrs older and has been picking on me my whole life) buuut, N0T something I recommend doing to your mom!
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Wish I had answers but I don't. All I can offer is my empathy and support