Relationships - my friend' had a breakup recently. she's in depression.I'm the only best friend she?

Talk to her on the phone, skype or whatsapp etc, i can understand it is difficult to not be physically there when she needs you, but you can always still help her out. It might take some time for her to get over it ofcourse but try to help her to stay positive and have hope till she does. Things don't work out because theyre not meant to be and there's something so much more better for you out there, even if you don't realise it now. If this relationship didn't work out, she will find someone who is meant for her. And there's so much in life to look forward to, friends and family, theres so much happiness in this world around her, just help her out to see.
I really hope this might have helped. I wish your best friend lots of happiness and love :)