I'm so sorry for your loss.
I don't have any advice (I think what the ladies have already said about covers it) But, I did want to say that it is completely normal for you to feel this way. You can be happy for her and sad for you at the same time. It doesn't make you a bad person. It might help to talk about it. Have you looked into local support groups?
I do agree, if you are honest with her, I'm sure she can understand. She might not understand the pain you feel. But I'm sure she can relate to being constantly reminded of something you are trying to move past.
~Big hug~