"Because he's beneath us, Tracey, beneath you," she replied calmly. "What will it do to your reputation if people find you've been spending mutliple nights with a halfblood? Using him once is fine, dear, but you can't let yourself get attached. Don't fool yourself into thinking he's more then he is."
Tracey may have already had a bit of a reputation to deal with as far as suitors were concerened, but this could be fatal to any hope she had of saving her family's dignity, which her sister seemed so eager to destroy.