Tough call brother. Personally I would not give an inch on this, because from my perspective you can never enable the delusions of other people as that only strengthens them. You have to rip the plaster off. Which means either walk away (obviously not that simple) or find the right words to break the spell they're under, which is easier said than done.
My father is still going to get his booster (4, 5?) despite my attempts to alert him to the potential danger of them. I don't think even breaking down in front of him would sway him unfortunately. It's so deeply rooted in his mind, like many people, because obviously it's not just covid, the vaccine, but the whole 'science' that underpins it.. to challenge it is just beyond some people's capacity unfortunately. "I'll take any jab I can get" is his philosophy

. I keep chipping away, by pointing out the contradictions and absurdities which I think is the best approach, rather than trying to force feed information. Get them to realize on their own by planting seeds and breadcrumbs that they can follow. It's manipulation, but they were manipulated into this delusion in the first place so..
If she's worried about her health then the greatest contradiction is stressing over this nonsense in the first place, which is more likely to make her ill than anything else! Unfortunately it's far easier to concede to fear than it is to have faith in your body and the fact you'll die at some point anyway, especially if you feel like your body has let you down already.
How to break the spell of fear and encourage faith. Sorry man, I feel your frustration.
EDIT: Tangent, but you might find the words of Dr Black Philip (Patrice ONeal) inspiring. His righteous attitude and philosophy towards women, admittedly used in a different context, is still applicable because ultimately it is about your happiness and the truth. He would probably take the position that you have to be prepared to take the loss on this if she is truly not going to sway, and holding that frame and using strong logic/language might actually focus her mind a bit. Certainly it would be more favourable to an outcome you want than just kneeling before her delusions.