Open Question: is it depression or something else?

Well, I want to know my sister is going through depression, or just hormones, or sad or something. She is very lonely and cried a lot Shes 14 years old, in the room there is a moderate, from school to the considerable pressure, she seems very happy to other people, but instantly knew that she did not receive much of her mood swings Shes got a lot of Recently, she ate a lot of headache! Most of the time, she could not get themselves to stop eating. With her low, there is no self-esteem, do not have much confidence that this is normal?