Hello DargaonGirl334, the best thing you can do for a friend that is really sad is to be there for her and help her through whatever issues she is willing to share with you. Never assume that everything is okay, by looking at her from the outside, sometimes people need to scream, cry, or write things down to get them out of their system. Be sure that you let your friend know that you are available to assist her with anything that she's having trouble with.
DragonGirl334