Hi. I am sorry to hear your mother is unwell.
I dont know if the flu shot could make your mother worse, altho I do react badly to vaccines
As it happens, I was treated for TA, two years ago. It was not unfortunately what was wrong with me! But, I do know a lot about it as a result. Any thing I can do to help or advise about TA , drop me a line.
I hope your mother feels better soon. Cath278