Unless religion is addressed in the divorce decree, BM is just as allowed to have her daughter confirmed as SO is to teach his daughter about evolution. If he does NOT want this to happen he’s going to have to get BM to agree to a modification that gives him religious decision-making authority. Not gonna happen.

Instead, focus on teaching SD about your world views and let her know that it’s okay for different people to believe different things and that these are just your beliefs. When she is older, she will make up her mind whether or not she’s staying the church, regardless of if she’s been confirmed. Most atheists in the US (I would venture) have been confirmed, it’s not a thing that ‘locks you in’ for the rest of your life.

BM is mom and is religious. SO is dad and an atheist. These are EQUALLY VALID systems of thought to share with their child, even if you side with one or the other.