Guys... my girlfriend needs help and i don't know how to give it

We are together for 4 months... at first i didn't knew that she has depression problems. Out first month was beautiful and after that... college happened for both of us.
At a point she went to a neuro doctor and he told her that she has depression and suggested her to go to a consultation with a specialist.(she didn't visited any specialist)
From there she started to be scared... because nobody understood her and said that her depression isn't real. (from here i was sure that she has depression... we never discussed on the depression subject because i don't know how to talk about it, i don't want to make thinks worse)
She is scaring me... i am sure she isn't suicidal, she is really smart and strong so you can take that out of the equation. But she is always sad... and for no reason sometimes...but this time it was real.
Tonight she lost her best and only true friend... i tried to convince her that it will be ok saying: "all you have to do is speak with her face-to-face", "you don't know if she really left you, don't jump to conclusions".(it didn't work,
the truth is that even i think she left her for real so i don't know if they will be back again)
She told me that she has no friends and has no hope to get others.(truth is that i was the only one that was close to her in the last month, the only one that understands her)

I want to know what to tell her and what not to tell her.
I know it will take time but i really want to help her, she is important for me.
Some info to give you a perspective
She is 20 years old
I am 21
Her father died when she was young (around 13 years old)
Please help... i don't know what to do...

I am pretty sure she will not go to a therapist, especially now. Maybe in the summer i will convince her, but until then all i can do is talk to her and be with her. I once told her to come with me to a doctor that can help her relax (it wasn't a psychiatrist, it was a family doctor) and she kindly declined.

A book would be a good idea but surly she will not be able to read it because the exams are coming up. Still, i will search for a book.

Any other ideas?