Mad at Mother-in-law

We were taking pictures for our announcement since all our parents would be in town and other family too. As we are still taking pictures my mother-in-law starts posting them to Facebook without asking! I hadn't even seen any of the pictures before she had posted them. When we were done taking pictures my brother asked if he could hit the "share" button yet, and I said no one post anything until I do. She still didn't take them down. I know once things are up on Facebook they can't be unseen, but it could have been fewer people she spilled the beans to. Am I over reacting that she spilled the beans before I could even announce my own first bundle of joy?