gender reveal ruined

I was planning a little gender reveal for our baby in the last 2 weeks counting down the days to our 16 weeks scan. We found out that we are expecting a baby girl :-). So we called my husband parents (who are abroad) and his sister and told them the good news. We were planning to do our gender reveal to our friends with some cute blue and pink pictures but my dear sister in law did a post on Facebook and Instagram with our big revel without asking us. We are very privat peoples we don't have any social media stuff and we prefer to talk to our friends or send them personal messages. But now everyone found out from that stupid post, my husband was so furious and disappointed. Everything is ruined, I'll still like to do the pictures but it won't be the same. I hate here right now she is so obsessed with attention that she ruined this event in our life. Do you think that I'm overreacting?