At a glance, the code for Annie's pregnancy shouldn't be any different from the other girls. But you say only Annie has been stuck like this?
I'll assume you didn't try to edit variables with the console or a save editor. Or that you used a save from someone that did.
The only thing I can think of is that you turned off the Pregnancy in settings.
Otherwise, I'd recommend joining the discord (linked somewhere at the top of the page) to get further assistance.