On a lot of different levels, this is not an uncommon situation for us. People like Elizabeth Koubler-Ross spent her entire life on this type of subject. She wrote books, gave lectures, and created many classes on this. One of her books is called Life and Death Transition. Look these up, you might find some answers. She is no longer with us (physically); but, of course, her books are. Another book by Jane Roberts called The Nature of Personal Reality can also be a help.
In order to understand this situation you've explained, it's necessary to come to terms with your ideas about death. I work with this type of situation, and it is highly sensitive because it involves deep beliefs. However, regardless of one's beliefs, there are very strong emotions involved. These emotions, if not dealt with, can become harmful to the self. They can also create great learning.
If you can be honest with yourself about how you feel about her 'death' you might discover that there may even be some anger involved. This emotion is usually pushed aside, simply because nobody wants to be angry about the death of a close one. The anger can be frightening. This is only one emotion that can come up with this; there are many.
These emotions are what we really need to come to terms with. One needs to be honest and courages with this. We are all always connected. The emptyness you feel is within your emotional structure. Your friend has not left you. It is only because of our lack of VISION that we feel alone and separate. I understand that what I am saying does not help your feelings; which are obviously quite strong; but, with some inner work, you can find a peaceful place within yourself, and know that nothing is ever lost, and we are all always connected. You can even look into your dreams for assistance with this. Your friend has always been with you, and always will be.
With Compassion,
Daniel