Ex wife involved in pregnancy announcement

My better half has a daughter from a prior marriage she is a only child at the moment. When discussing how to break the news to his daughter the ex wife asked to be there to see her reaction and celebrate with her. I find it inappropriate and an attempt to just have control or a say in my pregnancy. My better half feels like she has a right because she is her mom. I just need opinions am I over reacting in thinking it's wrong that I'm expected to be okay with her being involved with the announcement?