just me dumping everything like i'm in a journal

hi, i just want to know if i am being really ungrateful or i'm being walked all over. so here's the thing, its kinda hard to explain so i'll try my best

my sister would always get away with everything, i mean she would talk back (like in a bad way) to my parents, or when they give us a task idk like when we finish eating, we're told to clean the table and wash the dishes, and she would go and left me with all of it and my parents wouldn't say one single thing to her.

this two things sound very childish for me but like she's 13 and i'm 18, and she doesn't do a single chore and i'm getting tired of it bc i always wash the dishes, help my mum with the food or clothes, or literally studying bc i'm studying engineering and i NEED to study. and they literally needed to make my sister come from the school everyday bc she won't study and she was going to fail subjects from school.

(for context we went to a school where you can stay for the whole week and go back home for weekends or go back home everyday)

so i'm getting tired of it and when they told us to do something and she would stay in the couch w her phone i'm telling her to get up and DO THE THINGS THEY TOLD US TO!!!! and my parents would tell me to chill down and that i'm sarging (idk if that word exist i just google translated it but it's literally the word they use) her.

i'm gonna tell u what happened just a minutes ago, i know at first it doesn't make sense but j keep reading:

i have an uncle that lives in another country so he's here for a couple weeks and yesterday, my grandma told me that we were going to go to the shopping with my aunt, her husband, my uncle who's here, my sister and my grandma. It was not confirmed yet, but it was the idea. This morning i text my aunt to know when we were gonna leave (bc she would've go in her car and we were in another) so she tells me that when her husband comes home from work she was gonna tell me. all of my movements i would tell my sister so she keeps up. later my grandma and my uncle from another country told me they weren't going, so i text my aunt and ask her what we were gonna do, and she answers me that when her husband comes she would tell me if we were going or not. so i told my sister, and she literally just screams at me and says i wouldn't tell her nothing and that two minutes ago i told her another thing and that she doesn't understand. to this point, my parents were sleeping and obviously didn't tell her anything. later, my father wakes up and ask us if we wanted to go to our grandmas house (the same from before) and i told him that we were waiting to see what we were gonna do, bc if i was on my grandmas house and my aunt want to pick us up, she wouldn't go to two different houses for me and my sister. so i literally said "ana, let's go" so she could change (she was in her pjs) bc of what i said before. and my father screams too that i have to be more gentle with her and stop sarging (!!!!!) i'm like what i didn't said anything wrong and he keeps telling me the same thing. so i talk to my sister and told her to change bc we were leaving to my grandma's and she starts again to say that i told her a lot of different things and keeps saying a lot of dumb stuff screaming (!!) and my father literally shuts up BOTH of us, not her, bc she was the one that was screming, BOTH of us

i just really dumped everything the best i could so idk if it is understandable, but it is like this everyday, they would let her come out with it everytime and when i tell her something bc they wouldn't do it, they shut me up saying they are her parents and i'm her sister and i should support her and not give her orders. like WHAT if u don't give her orders (i don't even mean orders i just mean that u make sure she does what she needs to do) how are u trying to raise her.

i think the worse thing is that she always says "but you let her (me) do it" GIRL i'm 18 you're 13 there's things u can't just simply do bc you're not even a teeneger yet!!!! wtf

and they would say to me that i'm too childish bc i would get angry every single time and that i should be able to manipulate her so we wouldn't fight. that i'm too childish!!! i want to cry every single time bc they let her do things they wouldn't let me do and when i show a normal reaction to it they say i'm too childish and i shouldn't show any reaction!!

i'm gonna go crazy rn pls tell me i'm not crazy. or if i am please tell me too so i can change it