You're not a horrible person. You are a human being going through a tragic loss. You will go through every emotion that exists while dealing with this. It takes time. I had a very dear family member die very young. It hurt for a long time. Still does but in a different way. I'm not sure if you get over it or if it just becomes a part of you. I would find myself having long one sided conversations with him. It would help me put it in perspective. Finding a quiet place to let the emotions out helped too. Don't hold it in. Sometimes you just have to breakdown. Eventually, you will find that several minutes have gone by without thinking of her and then it will be hours. It will get easier but it will take time. Keep your mind occupied the best you can. Exercise to relieve stress. Try not to let yourself feel guilty when you do find distraction.
We're with you. Hang in there.
-John