Pregnant sister

So I am 17 weeks pregnant today. Last week we just found out that we were having a little boy. My sister is also pregnant with a little boy but is around 33 weeks pregnant. My husband and I were about to reveal on facebook what the gender of our baby was when my sister swooped in posting the gender of our child before we even had the chance to do so. She feels like she has done nothing wrong and my family also sees nothing wrong with it. 13 weeks ago she told me my pregnancy was most likely a false one, after my husband and I had been trying for awhile. She basically told me that I should just terminate. I am so fed up with her. I feel like this was so wrong but my family acts like im overreacting.