Hello there Jadey.  So sorry about your nan.  It always hurts to find you may be losing someone you love and it is never easy.  I don't think there is any way of planning how to deal with your feelings; they just happen and we have to deal them the best we can.  I would recommend (and I know how easy it is for someone not involved to recommend) that you try to remain your usual self while with your gran - she won't want her family's anxieties heaped on top of her own.  Try to remain cheerful, keep her company and try to find things that might please her - a few flowers, whatever - to show her how much you love her.  Play it by ear to a certain extent, take time to be with her and generally just make sure she knows how much is loved.  I know that none of this is groundbreaking stuff but if she is comfortable and knows she is loved then you are doing a good job.