Spalding, I'm really sorry for your loss. I recently lost my father, and the only thing I can tell you about grieving a parent is that it is unpredictable and goes in waves, and that anything you are feeling is OK. Just let yourself feel it. It is unreal. I could sit and look at the empty spot at the kitchen table and know he was gone and yet totally expect him to walk in at any moment.
Your sister's anger is also normal in grieving. It will pass.
I do hope you have support around you because you will need it. And I'm glad to know that you were there with her and that she knew she was loved and cared for to the very end.