It. Killing the vampire Faith. Even now, no one knew if having the swapped people still around would help their cause, but Claire didn't want to think about the fact that it might have helped and now getting Faith back would be that much harder. The vampire had been killing people and they hadn't been able to stop it, there had been no other way. She had to keep reminding herself that Faith wouldn't have wanted anymore blood shed in her name.
Though she could have offered her own opinion, the question Sam asked was addressed directly to Dean. Claire, sensing a break in the no-talk situation of late between the brothers, decided to encourage it. Squeezing Dean's hand, she got up and made her way around the couch to head for the kitchen, within earshot of what was going on, but feasibly doing something useful as an excuse by getting Dean some food.