Thank you for writing.
The Joanna Budwig diet is to help with cancer but also with chronic illnesses, to my knowledge - but I do not know if it will necessarily help with an inflammation that is caused by bacteria or some sort of virus (pathogen). I know know enough about the diet to say. It would take days to read her diet book and other publications for anyone to form an opinion and then weeks to see if changes occurred as a result of adopting the diet. As long as the diet is well-rounded and healthy, I'm sure it can't hurt.
I do know that the FODMAP diet can help with inflammation. Nutritionist Kate Scarlata has a website I encourage you to look into.
Regarding magnet mattresses, the studies I have taken a quick look at indicate there is no proof they actually work, other than provide a placebo effect.
Diet is an important part of treating inflammation - I suggest your friend sees a nutritionist who specializes in this, rather than gathering lists of foods. Her doctors can point her in the right direction.