One of my daughters has a slight tremor since the booster. She says she has long Covid... has never connected it to the vaxx. Your friend could do the vaxx injury protocol at the flccc website:
https://covid19criticalcare.com/
That’s a good website. But it’s very difficult to convince them to take advice from an alternative web site. The only valid information to them is what’s in the mainstream. I’ve been asked where are you getting that information from in a condescending tone. When I get that I just move on.