Hi Marie,
The same situation happend to me last year. My sister in law was pregnant at the same time I was, and it was her first baby. I ended up having a partial molar pregnancy, and had the D&C about 2 weeks before her baby shower. I kept trying to be brave and telling myself and everyone else that I was happy for her and that this wasn't about me, and therefore I was set on going. I realized afterwards that it probably would have been best to sit that one out, everyone would have understood. I was too hard on myself and the shower was just horrible!! And kind of embarassing since everyone there knew what I just went through, it was uncomfortable for me and other people. Had I known then what I know now, I wouldn't have gone and it would have been okay. Good luck with whatever you decide to do. I just think sometimes we can be just a little too hard on ourselves!!
Michelle