Ya so whilst starting new game I got to the second floor of the prison just fine by myself until I could get Yoshimo. But accidentally sent him on his way and reloaded the game to get him. When I loaded the auto-save at the Portal the window pans allll the way back to the prison cells where you start out and there's Imoen! She says "You're not gonna leave me here by myself, are you"? So I get a second opportunity to accept her into my group - which I do. But directly after I ask her to join she begins this HUGE dialogue about the entire dungeon area by area. So I'm like ... wtf? Well she finally shuts up and then I have to walk her through everything and then get her to the portal, too. Yay!
Yeah that was kinda stupid. But I'm assuming that was a bug. A bug I FOUND.