AITA for refusing to look after my niece due to her lying and being violent?

I'm 28 and I have a sister (35) who has a daughter (8) who we'll call Suzy. My sister is a widow but is in a relationship with her boyfriend (33).<br><br>Suzy has a tendency to lie and cause problems for people. She'll lie to get people in trouble, steal food when she's been told to not touch anything and is generally violent. My sister has tried to get her help but nothing seems to work. She's been kicked out of two schools due to her attacking kids and is currently in a special needs school due to her autism being severe. <br><br>Last year due to my brother in law dying suddenly, Suzy constantly said she wanted to die. She said she wanted to kill herself multiple times and my sister did get her admitted to a psychiatric hospital on 2 occasions but it didn't do much. The hospital did say to my sister she needed to stop coddling Suzy and be stricter. My sister has a tendency to excuse Suzy's behaviour due to her autism even when doctors have said it's not due to her autism but Suzy just being a shithead.<br><br>My sister and her boyfriend are wanting to go on a holiday for a week and because all of her friends are unwilling to look after Suzy, she asked me. I said no because while I take care of Suzy occassionally, leaving her with me for a whole week is too long. I also don't want her at my house as she'll touch my stuff and break it. She'll also destroy things to the point my landlord could get involved. I told my sister this and said I would rather not have Suzy staying with me.<br><br>My sister got angry and said she has no one else to ask. I told her to cancel the holiday but she said her boyfriend would break up with her if she did. I said there was always next year and she can take Suzy with her. She said Suzy wouldn't be allowed and the holiday was already booked. <br><br>I ended up relenting and said she could leave Suzy with me. I just told her that if anything went missing or was destroyed, I would be telling Suzy's father's family and they would have to pay for the damages. My sister agreed but when she went to pick Suzy up, she got angry at me for asking her to pay for anything Suzy destroys. She said she's already having to pay for thousands of dollars of therapy, medical bills for when Suzy was admitted to the hospital, lawyers fees due to Suzy attacking kids at school and being sued, replacing Suzy's school uniforms that were ruined, replacing broken tablets and phones, etc. <br><br>She said I had no right to ask her to pay for anything Suzy ruins and that I should be helping out. I told her no because none of my stuff was cheap and I pay a lot for my rent. If Suzy ruins anything, I'll have to pay for it which I can't afford. My sister told me I was being petty and I was letting our family down. I told her I was just protecting myself and she was being stupid for taking a holiday when she has a child that clearly needs her. <br><br>She then told me that I was being selfish, immature, unhelpful and just a bad person in general. She said I should be helping her out instead of refusing to help. I said she was being a bad mother if she kept letting Suzy get away with this. I told her she needed to actually discipline Suzy instead of letting Suzy destroy my stuff.<br><br>My sister told me she was going to go stayed with our cousins instead and that I was off the contact list. I was a bit annoyed that she's calling me selfish when Suzy is the one who will end up destroying my stuff. <br><br>AITA for refusing to look after Suzy even after my sister offered to pay for anything Suzy destroys?