First of all, I hope this is a serious post, because that would be pretty low if it isn't real (I have seen many fake things like this, and it always irks me...sorry if I sound like I am attacking you).
But when people must face their own mortality, every person deals with it in his or her own way.
Some people surround themselves with loved ones, so that they can reflect on the postive times in their lives, cherishing the time and the memories they have of loved ones. The best thing you can do be there for her whenever she needs. Maybe throw a party or have a gathering of loved ones, so that she knows just how much she is loved. BUT (!!!!) please do it tastefully. There is a fine line between gathering friends and family to celebrate her life, and throwing her her own premature wake. Be careful, if you decide to take this particular peice of advice, to try and judge how she would feel about this. Sometimes, it may just be too much, and might cause her stress and sorrow. Try and get an idea of what she thinks, without asking "Do you want us to throw you a party?" Be tactful and respectful.
Some people try to keep themselves busy, to occupy their mind. Get them out there and keep them engaged. Go outdoors, or any other hobbies she may have. Keep her interested without making her feel rushed or like she is a burden. Offer up suggestions of places to go or things to do and let her decide.
On the other hand, some people are more introverted and like to reflect. If that is the case, it is usually best to give her some space and let her deal with any issues and feelings she may have. She may need to sort out her feelings before you can help her. But, always be there for her when she reaches out and needs someone. Give her space but don't abandon her.
She may also need all/none of these things. Like I said, people cope with stress differently, and so it is up to you to judge what she needs the most and be there to support her. What I mentioned above are just suggestions based on some basic personality types, but people are much more complex than that. Some people may need to be surrounded by loved ones one minute and then want everyone to leave them alone the next. Respect how she feels and try to do everything you can to help her through this.
The best advice I can offer is to be a good friend.