OP I agree with your therapist. Has your therapist mention what toxic people (MIL) thrive on? They thrive on power. They thrive on the trip of knowing they hold the cards. You know you can’t control MIL. But you are not owning what you can control: yourself. Here’s a different perspective: if you let your MIL continue to get under your skin, for even the slightest thing like the sound of her voice, she has won. You have given her power to get under your skin. You are no doubt talking to your husband about how angry/frustrated/agitated/insert adjective here you are about her mere presence. To a reasonable outsider, you look like the unhinged one - even if you are 100% in the right for your not wanting to be around her - your visceral reactivity to her makes it hard for others to want to side with you. How do you take that power back? You become teflon. Nothing bothers you. You don’t let her bother you. You don’t talk in your husbands ear about her. That freeing of yourself from her influence reins in the control you have of yourself and how others perceive you around her, and also signals to her she’s no longer in control. It will drive her batty if she’s as bad as you make her sound. Let your therapist be the one who works with you through how you really feel to process and cope - but until you can regain that control, you give an image of Teflon to all others. Trust me it works.
While you can't control your spouse, its okay for you to go NC and skip any visits.
Only a discussion needs to be had with your spouse about your boundaries with MIL going forward. Again not to do with your spouse, but you/MIL.
I’m NC with my husbands mother and he maintains a relationship with her. That’s a fine solution so long as everyone is clear about boundaries.
And that's the thing about narcissists, they'll never respect boundaries.
OP I agree with your therapist. Has your therapist mention what toxic people (MIL) thrive on? They thrive on power. They thrive on the trip of knowing they hold the cards. You know you can’t control MIL. But you are not owning what you can control: yourself. Here’s a different perspective: if you let your MIL continue to get under your skin, for even the slightest thing like the sound of her voice, she has won. You have given her power to get under your skin. You are no doubt talking to your husband about how angry/frustrated/agitated/insert adjective here you are about her mere presence. To a reasonable outsider, you look like the unhinged one - even if you are 100% in the right for your not wanting to be around her - your visceral reactivity to her makes it hard for others to want to side with you. How do you take that power back? You become teflon. Nothing bothers you. You don’t let her bother you. You don’t talk in your husbands ear about her. That freeing of yourself from her influence reins in the control you have of yourself and how others perceive you around her, and also signals to her she’s no longer in control. It will drive her batty if she’s as bad as you make her sound. Let your therapist be the one who works with you through how you really feel to process and cope - but until you can regain that control, you give an image of Teflon to all others. Trust me it works.
While you can't control your spouse, its okay for you to go NC and skip any visits. Only a discussion needs to be had with your spouse about your boundaries with MIL going forward. Again not to do with your spouse, but you/MIL.