First off, please accecpt my deepest sympathies on behalf of your friend. Having a loved one die is always hard no matter the age.
Secondly, the best thing that you can do for your friend is to "be there" for her, either by your physical presence or by listening to her on the phone.
If you can go to her, then make sure that you can stay there long enough to help her through the funeral as well as a couple days afterwards. There is going to be so much activity going on to keep her mentally busy...but once all of that quiets down, then she is really going to notice the loss.
One of the best things that someone did for me after I lost a loved one was to send me a Thinking of You card a couple months after the loved ones passing.
Hope this helps...