My sister is pissing me off, what should I do?

Anonymous
My older sister is 19 turning 20 very soon. She still lives with my parents and I. She was supposed to go to a medical school to become a Vet Tech a year and a half ago, but instead, she's been working at Starbucks. She has her boyfriend over all the time and he practically lives at our house. He's sleeping over, using our shower, and he's made his own food in our kitchen more than twice.

Sometimes, and even more recently, she's acted bossy towards me. Say for example, which happened just now, she came home with her boyfriend (of course!) from hanging out with friends and she's yelling at my brother for being awake at midnight. Come on, it's summer time, and what pisses me off is that he stays up all the time and my sister doesn't say anything about it until now?

Then she yells at me for no particular reason, and then they both go to the bathroom together. Then she yells out stubbornly, "Who left the door open?" and I said it was I, and she said "remember what I told you about leaving the bathroom door open!" and she took the bathroom trash can and she went into my bedroom and dumped it all on my bed.

That bitch! I swear to god. I explained to her that I've closed the bathroom door all day after I was done but just not this time, I forgot. But she wouldn't hear me, instead, she proceeded with dumping the BATHROOM trash onto my bed.

She wants me to keep the bathroom door closed because our kitten keeps getting into the trash. And I did, all day, but of fucking course the one time I forget my sister comes home and that trash can shit happened.

What also pissed me off, is was when I was out with her friends, and when I accidently talked a little loud when we're outside at a park at 3 in the morning, she walked over to me and slapped me really hard on the back. In front of her friends. And sometimes when I'm talking and I say something that sounds stupid to her, she'll tell me to shut up.

There are other stuff but I'm out of words. So, Advice?
My sister is pissing me off, what should I do?
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