It was Angie's place, wasn't it? She was only staying at the house so Joe wouldn't be there alone.
I can buy that; it would kind of explain her apologizing to dead Linda, too.
There's probably a huge net at the bottom of the pit and it's going to turn out that Sam is Dauntless and the Dome is actually part of the Divergent story. Veronica Roth will come in and write episodes of season 3 and Chester's Mill will magically become a suburb of Chicago.