Make an argument that the look of fear on Tav's face when kissing AA is justified. What specific dialog lines in the game do you want to tie them into?
I think it would work great after attempting the first breakup in the AA route. Any of the explicitly very negative paths will do. At this point, the romance is ripe enough for that kind of path, though I stand by my general criticism of the game -- most expressions are overplayed.
In total, if you break up with a vampire because you think he has become a monster... yeah, you're probably afraid playing as Tav, though the faces still need polish.
