You got it.

First of all, I'm of the opinion that your sister's clandestine move to skew the ratings against you and subsequently for herself was deplorable. Not only is it just flat-out cheating, it's a complete smack in the face to the very essence of the whole thing. She let her jealousy get the best of her, and like most people who let that happen, she tried to rationalize it (and failed miserably).
Furthermore, although you did put up pics of your breasts on a public site, where your mutual friends could have stumbled upon them without invitations sent by your sister, that action is shameful as well, and only exacerbated the problem.