reveal drama

I am pregnant with my second child and am very excited. My husband and I have decided this will be our last baby. I am going to find out the gender on the 10th. My sister inlaw has informed me she doesn't want to know the gender of the baby. I'm upset because I have been so excited about the gender reveal and now feel like I can't put it on Facebook or enjoy it the way I wanted. Is this me being emotional or is she being selfish?