I'm still going to go with Talana's dying spirit intermingled with Thingy's, starting off as one of them and gradually becoming the other as one died and the other's influence became more dominant. Either that or my other theory that it was always Talana all along, though that admittedly doesn't properly or convincingly address the dragon memories and morphing thing. But either way, I still think that Talana was effectively possessed by her right from the outset.
And boo, you've pre-empted my albeit rather tardy attempt to decipher her accent! Which is a fairly neutral Black Country one so it doesn't really take a lot of deciphering. Actually I did like the amount of Brummie (and thereabouts) accents ED had. And I'm still entertained by that guy you encounter in OS2's Nameless Isle who refers to you as "yow".