What can be given to an 80-year-old person for lack of appetite?

To @Andrzej: First of all, you can try to give your mother products based on valerian or lemon balm, which make it easier to fall asleep. It is worth talking, encouraging to eat meals - often, in small portions. If within a month or two the situation does not improve, it is worth consulting a psychiatrist.

In December, my father died and my mother's husband died. Mom does not sleep all night, she is very nervous and almost does not eat, she loses weight very much. Is it necessary to visit a doctor or are there any dietary supplements or other drugs that will help her in such a situation?