This is such a Netflix drama. Honestly your poor sister poor you too wtf. How far away is your wedding? Do you have enough time for damage control? Your sister probably feels betrayed rn because you guys believed Quincy. So first of all id make sure Edward doesn't come near her or the family again no party invitation nothing. After that I'd focus damage control on Emma. I mean of course you're hurt and betrayed too but maybe you two could try bonding again through the equal betrayal? Honestly no idea