I am a 50 years old female just diagnosed wit vey low platelet 4000 the doctor prescribe prednisone to her is that a good option?

Life Threatening: Yes. A platelet count that low is life threatening. Prednisone is often part of the emergency treatment to protect your life.

Possibly, yes: Thrombocytopenia or low platelets have a variety of causes. It may be immune mediated or Idiopathic which means we don't know the cause. (ITP). It can be transient, acute or chronic or recurrent. It may be associated with hematologic malignancies as well and a bone marrow biopsy may be need. Prednisone is often the first line treatment and plasmapharesis, vincristine and gmcsf are sometimes used.