What Causes Vertigo And Excessive Weight Loss?

My dear friend , female, age 75, has chronic vertigo, made worse upon standing. She has lost a great deal of weight, handwriting has become almost illegible with very small letters, weak, with shuffling walk, a wide-eyed stare, nervousness, disinterest and apathy. This has been going on for about a year, with visits to cardiologist, endocrinologist, neurologists and internists. Several tests have been done, with no significant results. She has been prescribed anti-anxiety and antidepressant meds, but nothing is helping. Any suggestions or diagnoses?