Post covid effects Vomiting and giddines

Hello, My sister got covid 5 weeks back and from 4 weeks, there is continuous vomiting once a day daily. She has become weak and lost weight from 62 to 55kg. Also she is having frequent urination. We consulted urologist and found mild urine infection and gave course of antibiotic tablet - taxim. Still the issue perissits. We did endoscopy and found there is no problem. Doctor said mostly depression and gave placida. When ever she has food she kind of gets dizziness with bp drop and she is back to normal in 10mins of lying flat. We are not sure what doctor to see now. We met general physician, Urologist and Gastroenterlogist doctor. Should we consult neurologist. What could be the problem of giddiness, frequent bp drops and vomiting after 4 weeks of covid. It would be helpful if someone guide us on which doctor to consult And cause of such occurrence.