I want to slap my sister because she got intimate with our mom's boyfriend.
While that's very shocking, slapping your sister is just as bad.
I don't like her, she's always rude to me
While it is okay to be upset at your sibling for acting inappropriately, it isn't okay for you want to physically assault your sister since it is illegal and can lead to health issues. Instead of letting out your anger through violence, you should try to resolve your issues with your sister through discussion. You should let your sister know that what she did was inappropriate and that she needs to talk with your mom and apologize for what she has done.
The bitch better do what I say. be a nice sister and answer my questions.
I do not think that language and violence that you have shown with your sister is going to be healthy for you both. She may actively avoid you in the future and you may need her help one day and she may refuse to do so because of how you're treating her now. She has made a mistake, but you shouldn't treat her with toxicity and anger all the time.