baby announcement hijacked

Annette
So I'm trying not to be upset... but I am. Yesterday was Thanksgiving. And my husband and I decided to tell his family we were expecting. We had told my parents the week before and My mom asked if she could tell my whole side of the family on thanksgiving too. I really wanted to but said I was  ok with it because she was so excited to be a grandmother.
On thanksgiving we called my sister in-law who lives halfway across to country to tell her the good news. She blasted it on Facebook. She was really excited and had nothing but good intentions but I kind of feel like it was taken away from me. I had a whole announcement planned to put up next week. How would you feel ?