My (16f) autistic step-sister (f19) had a fit and ruined a lot of my things. My parents refuse to punish her and I don't know how to get over it

So my step-sister "Cara " has been my step-sister for a little over 3 years now. She's 19 but according to her dad/my step-dad she has the mentally of a 7, maybe 8 hear old. She has really bad impulse issues, she's been arrested for shoplifting before. She still sometimes has accidents and wears a diaper overnight. She has fits where she will just flip out over some small injustice and destroy everything around her. It's been really tough to live with her but she is on several medications and has several therapy appointments each week

So with my step-sister having all of her issues, I've had to get summer jobs either baby sitting or dog walking to pay for my own things. My mom stopped buying my school clothes for me when I was 14. This year I was finally able to get a real job working at my movie theater. It's not great and I make minimum wage but I was able to save all of my paychecks and buy myself a lot of new clothes and makeup.

What started the argument we had last night was my step-sister wanted to try on some of my clothes and I said no. She went and tattled on me to my nom and my mom came into my room to tell me to let her do it. I said no, it's not fair for her to try on (and eventually take because she's done this before) my clothes when I've paid for them. My mom said that I can just buy whatever I want over again since I'm working. I guess our argument triggered her sensory disorder and she flipped out. She punched my mirror and shattered it, cutting her hand really bqd. She kicked a hole in my wall and was starting to cry and scream. She picked up my makeup bag and threw it across the room where everything in it broke. She lurged at me and my mom had my step#dad come in to bear hug her and calm her down. She ended up having to go to the hospital and get stitches in her hand over how hard she punched my mirror

My mom and step-dad blame me over it now that she's home. All of my new clothes are now in her room and instead of being happy she got what she wanted, she poured bleach and toothpaste all over them and now her room stinks and smells so bad. My parents want me to pay for her hospital bill now

I don't know how to not be angry. A lot of my things were messed up. I didn't mean to trigger and upset her but I just didn't want her messing with my things. My parents are still mad and tell me she can't be held responsible because she's disabled. That I should just give in and let her do what she wants to do. I don't know how to move past this. I could really use some advice on this

Tl;dr: autistic step-sister had a melt down and destroyed a lot of my things. Parents blame me and say she can't be held responsible. I'm just upset and don't know how to get past it

Submitted June 20, 2019 at 04:48PM by PhysicallyEm http://bit.ly/2XZK8k1