Right i know how bad this sounds but try and understand my reasoning.

Basically it started when my nana planned a day to go swimming with me and have a day just to ourselves. Some really bad stuff has been happening lately and I've been feeling really down so my nana suggested a day to ourselves to make me feel better. 
Usually my nana and I watch my sisters on a Wednesday so we asked my Papa to watch them for a few hours and he said that's fine but not for my sister L, (L has always been a bit of a brat since she started hanging with the horrible wee girls who made fun of my youngest sisters autism) 
L threw a fit she said if she can't come she is going to her friends and tried to leave the house my poor nana had to lock the door, she came in and threw water all over my room and then threw slime at me and it went everywhere and I had to do all the cleaning. (Also she knows I hate slime and can't touch it cause it's freaks me out what is one of the perks of me having Aspergers)

Today she pushed me over the edge when I realized I got my period and it hit hard, blood was running right into my jeans so I rushed to the toilet but L pushed past me so I tried stopping her and said "L stop I'm on my period and I'm bleeding through" she looked at me laughed, Locked the bathroom door then said "but I'm already in" she proceeded to take as long as she could in the toilet, probably about 10 minutes. By the time she was out blood was all over my white jeans and I was fuming.
So I got a pad went and changed my underwear, changed my jeans for leggings. 
My bloody jeans where Inside out so the blood was alot more visible I took them, went into L's room then did a perfect throw from the door to smack in her face. She looked shocked for a second, looked at me then looked at what hit her then screamed, like those movie scenes screams where wine glasses explode she also started crying and mom came in thinking she fell or something and then shouted at me although I couldn't stop laughing.

Do you think I went a bit far?