My girlfriend's depressed and she won't tell me why?

Ok my girlfriend and I (she's 16 and I'm turning 16 on the 18th) have been dating for about half a year but after about 1 month she moved to Washington (the state) and I live in California....... do u see where this is going? A whole bunch of ****'s happening to her all the time and I want to know why so I can be there for her and tey to make her feel better. The problem is I CAN'T be there for her cause she lives a state away and it's killing me cause I know I could help if I was actually with her. idk what to do I want to help her but i can't and that's the thig that keeps me up at night worrying about her all the tine somebody please tell me wha to do (if u tell me to dump her i will kill you and everyone u love........ that's a joke)