How do I act if my sister who I hate with the force of 10,000 suns ends up coming to a family event or my birthday?

just stay away frorn her

Well, for starters, you DON'T act like a drama queen. Hate with the force of 10,000 suns?? Oh, please. You don't enlighten us with any information about the terrible, horrible, no-good, very bad thing she did to you to turn you into your scathing little self, so how can we know how you're supposed to act? A novel idea might be for you to act civil and mature instead of pitching a fit. You could say, "________ (her name), you're looking well today". Then move on and start talking to someone else. If she feels the same way toward you as you do toward her, I don't think you have to worry about her showing up.

You put on a happy face, and make the best of it - while trying to stay out of her orbit at the party so you don't have to interact with her too much (if any).

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