Sorry to hear about your friend. There are several supplements and other approaches (such as remaining active but avoiding strenuous exercise) that have been reported to help those with post-COVID and/or COVID "vaccine" symptoms.

I'd consider, as a start:

Nattokinase -- an enzyme reported to deactivate / protect from the spike protein, which is a key driver of inflammation and injury from both COVID and, even more severely, the "vaccine." It has been widely used for decades (for protection from blood clots, inflammation control, and more) and has recently been recommended by well-known doctors for those suffering from spike-mediated damage. There ARE contraindications and possible side effects, however; browse https://www.qwant.com/?client=brz-brave&q=nattokinase

Taurine -- an amino acid that supports cardiovascular health and has recently been getting press for improving overall health in animals and humans and actually extending lifespan in animal studies. Your body already makes this, but production falls as we age.

Vitamin K2, and in particular the MK-7 fraction of K2. Here's a good source: https://www.lifeextension.com/vitamins-supplements/item02334/super-k. Anyone on blood thinners should talk with their doctor before starting vitamin K supplementation.

also: Vitamins D, C, the B vitamins (as in a good multiple, although I'd also take addition D and C), and supplements that reduce inflammation; see here for some information.

I'd add that the "vax" in particular also weakens the immune system, which can lead to any number of diseases including cancer, so if I were jabbed I'd be sure to do everything I could to support my immune system with supplements, careful diet, moderate exercise, stress reduction, and so on.

Best wishes for your friend.