So sorry you’re dealing with this!
I would just really encourage her to just listen to your doctors. And, if it helps any, I am fully vaccinated with Pfizer and have a grade 4 AVMs in my left arm.
Also, remind your mother how much more important it is for us to be protected against COVID since this disease could effect us so strongly! An inflammatory disease is honestly my worst nightmare as a person with AVMs and would rather the possibility of vaccine side effects than the definititive outcome of contracting COVID.
Hope it helps and that you get vaccinated ASAP!!!