Because she really did have her memories wiped and Tav would be taking advantage.
But you can't even have the cute date scene with her if you side with the goblins because she drinks herself into a stupor.
And now I know what the truly evil character will do, of course - perfect opportunity to take advantage.
It is strange to shy away from that path if the character is evil (although it is ok to take numerous lives and remain a good person by the game's definition, it would seem). Hypocrisy rampant.
