Chastity appears very early on in Act Three, and it's just for a quick event. There's no way to get her to join permanently just yet.
I'll take a look back over the code to see if there's anything that could be preventing her trigger from activating but if you're using an unofficial version (eg. a translation) then there may be bugs with it.
As for the train station and the church, you can't conquer them yet (for the reasons revealed when you tried to conquer the other side of the bridge).