Saw this under comments for the booster.
"They definitely are necessary for the immunocompromised. I have a friend who had a kidney transplant two years ago, and even with both doses of the Pfizer vaccine AND both doses of the Moderna vaccine, her antibody count remains dangerously low."
That's how it's going to be if she can't make antibodies. Her body won't make fake ones either. Probably she is unusually anxious, wishing she could do something.