Before anyone calls this bullshit, I wanna say that I am actually confused about this whole situation and I really need an opinion from outside of the story. Emotions are still flowing, so if I let anything out I'll edit the post.

So, for context, I used to have my own PC, but it stopped working recently, and it's on repair. So I either don't use a PC at all or use my dad's notebook, which usually is not an option because my 5yo sister (I'll call her "Sam") is using it ALL THE TIME. Whenever I ask it from her to use for a while she either yells "NO" or cries for my parents' attention, and they never did anything about it. Eventually I gave up and stopped asking.

Ok, so today my mom went out with her, and I had the notebook for myself the whole afternoon. My mom gets back, we talk about college for a while, and then I let Sam use the notebook for a few hours. 

When Sam went to her bed, I was about to get back to the notebook again when my mom asks for it so my sister could use, cause she didn't want to sleep. I got mad and asked my mom why, cause they always let her use it and I never get the chance to do anything. She basically got mad too and started calling me names and answered my question by saying "because I want to".

Things escalated quickly and she started pushing me against the wall while still calling me names (I can't say I stayed calm either, I was trying to defend myself/minimize the pain by pushing back a little bit, I had no intentions in hurting her and I'm pretty sure I didn't).

When she released me I kinda felt bad and decided to give her the notebook and guess what? My mom didn't accept it anymore, got really pissed and tried to tell my father what happened. She said that "I no longer existed to her", and tried to justify that with her version of the truth (that I was the one trying to hurt her, that I "grabbed her arm", while completely ignoring what she did to me.) I called her out and added the details she "forgot" and my dad actually stayed on my side for once and said we would talk about that tomorrow.

So, basically, AITA for not wanting to give Sam the computer or should I give it to her even though she already uses it all the time? Honestly I think my parents are going too soft on Sam and have been going for a while (this time just my mom, dad actually stayed on my side for once), but whenever I say something they ignore me, since "they are the parents, they decide what's best for their children".