I think fridge!Amber doesn't bother me so much because she got to have a proper character arc of her *own*.

It doesn't bother me very much, either, but it does bother me at times because I'd rather have her alive and kicking ass. *sigh* In a sense, every character on the show exists to serve as House's satellites, so the fact that Amber too would die to further House's characterisation makes perfect sense. And it really was a kickass story arc, the first proper story arc the show pulled off, and that makes me happy.