She was definitely more plot device than character in this half-season (or at least, the plot device aspects were badly obscuring the character). I don't, to be honest, pay much attention to the back-stage information that comes out of Cardiff these days, so I've no idea whether the official line is "this is what we planned all along". Season 8 felt like a do-over and start-from-scratch character-wise to me, though I'm seeing similarities now but its difficult to say whether that is simply a result of jettisoning the plot device stuff or whether it was triggered more by a recognition she'd been poorly served and a need to delineate her more clearly.