Just don't let her know you're going into labor and don't tell her either when the baby comes til after! If she's going to be difficult and not respect what you guys ask of her with something like this then she doesn't need to be in the immediate loop. I would tell her as I'm getting ready to publicly announce it so she can't beat you to the punch. Sad that it even has to be that way :/

Just tell her that it's best that she wait to post anything. You as the parents should be the first to share the happy news. If she doesn't go for that, then just don't tell her until you have your little one. Hopefully she'll understand and follow your wishes.

@chocohunnybees, we are gonna try talking to her. but she attends not to care what we want. so hopefully she'll listen.

or, keep her out of the loop

Then have your fiance tell her.

@chocohunnybees, i wish it was that easy... but my Fiance mother and I don't see eye to eye.

just tell them.