My mother is 72 when she stands up for a little while she wants to pass out?

My mother is 72 and was generally healthy until few months ago…she had breast cancer 8 years ago but is in remission….she have done tests yearly….in April she had an light stroke….afterwards she seemed fine, but now she is very tired all the time and when she stands up for a little while, she wants to pass out. She loves coffee, but suddenly developed a very strong aversion towards it…so bad that if she smells it, she want to throw up. She also has a very bad constant cough. She did blood tests, but everything came back as normal and the dr said that they did not find anything wrong…..they tested for iron and magnesium deficiency, thyroid function and a full blood count…they also tested for cancer…I am very worried about her because something is definitely wrong….and now she does not want to go back. Can you please tell me where to go next