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I'm sorry that your sister reacted the way that she did! I understand you not wanting to talk to him much/at all if he is a bully and a predator! Maybe you can explain to your dad why you requested that if he doesn't know already.
I'd let things cool down before you talk to your sister if you plan on it. I know you only have a few days to talk to her on, but maybe you can try to clear the air with her before Thanksgiving and see if they'd still come over, for family's sake. I wouldn't go back on your stance that you don't want to interact with him much and maybe don't bring that part up, but you can tell her that you'd still like to see her on Thanksgiving.
Having her ask your dad from now on may be a good solution. He can then tell you whether or not her stepson is coming over so you can prepare ahead of time for that.