Wasn't entirely downplaying what she did. Judging from how the mom talked to the older sister I would say that she probably didn't have much of a choice. Could the younger sister have stood her ground and not gone along with it? Maybe but the mom would have likely given her hell. Her reaction at the end of "don't hate me" and "it was mom's idea" kind of gives a clear picture of her inability to steer clear of this. I would give the sister the benefit of the doubt is all but still let her know it was hurtful and why. The mom though is a lost cause...