I Have A 55 Year Old Friend Who Refuses To

I have a 55 year old friend who refuses to get a flu shot each year because she's says it has mercury and that causes Alzheimer's disease. Can you tell me if there is any mercury and if so, how much? And what study, if any, could she be referring to? By the way, I'm 66 and get a flu shot every year....and my friend thinks she has the flu!! That's why I'm asking now. What are the facts that I can present to my very stubborn/skeptical friend? Thank you!