I understand and appreciate your question.
Weakness, fatigue, light headedness, hard to keep food down, tired, shortness of breath
, sweaty, cold, are all signs of anemia.
Black and blue marks on her legs, maybe is a subcutaneous spot of bleeding.
Bleeding from stools( or digestive bleeding) and subcutaneous bleeding, are both not a disease, but symptoms of a disease.
Also anemia may be a sign of another disease that has caused anemia.
The diseases that can be suspected are; Thrombocytopenia
, disseminated intravascular coagulation
of liver disease, drug-induced platelet dysfunction
, hyperfibrinolysis, acquired clotting factor inhibitors.
In the case of your niece maybe having complaints due to bleeding, the first priority is to identify the most likely cause for bleeding and selected treatment based on the cause of bleeding. In this case detailed examinations are required to determine the diagnosis.
Thank you for asking your query on health care magic.
If you have more questions, feel free to ask.