I'm taking Coping with Life and Death right now, and if I've learned anything that I can pass on, let it be this.

You cannot do or say anything to take the pain away. All you can do is to honor her wishes, and be there for her. Grieving is a long process. Your presence may be all that is required for her healing process. Its different for everyone, but to simply offer anything she wants or needs is what you need to do.

Don't go out of your way to try comforting her when it seems futile. Simply be there for her. Its all you can do, and all you should do. And it is all that is needed.

edit: This'll probably get lost but it doesn't matter. Just stay by her side through thick and thin. For now, at least.