So these pictures are what you USED to look like--but you don't look that way now. That actually would be something you should be proud of, that you were able to overcome your former anxieties and you're now attractive and feeling good. You've also attracted a person who obviously loves you and you have a future planned. Here's what you do--you tell your fiance that you have a promise to make to him. Show him the pictures yourself, and tell him that you promise because you're so happy to be with him, that you will never look that way again. You're dedicated to looking and feeling good, and he's given you the incentive to do that. You need to trust that because he loves you, he will stand by you. Then, if the mean sister does try to blackmail you by posting the pictures online, you can file a lawsuit against her for breach of privacy and attempting to blackmail you. If she wants money from you to prevent her from posting them and she texts you about it, save the texts, and you can take her to court and win. You don't have to tell her you've already told your fiance. If she tries to send the pictures to him, let him deal with her. You need to believe in yourself and believe that he loves you as you are. If he truly loves you and wants to marry you, what you looked like years ago doesn't matter. It's who you are now that counts.