My family is all calling me horrible right now so I thought i might as well risk the internet doing it too.

So, tomorrow my sister will be kicked out of her apartment and will most likely have to live on the streets if she cannot get into a shelter (there are very good reasons she would be turned away from a woman shelter.). And I could have prevented this.

I'll start by saying I don't like my sister. I wouldn't say I hate her, just don't like her. She has been a constant force of negativity in my life. She borrowed over 5k from me in college and never paid me back. And then totaled my car while drunk, causing my insurance to drop me and refuse to pay anything. After this, I cut her out, For over 5 years I have ignored her entirely. Outside of family events and proxy connections through my mom. I have refused to even acknowledge her existence.

Well, she moved out to the other side of the country in January. She went there to live with her boyfriend and her daughter. From what I heard things got bad quickly with him and she had to move out and live on her own. Sometime during the summer she lost the job she had gotten and hasn't found work since. Because of all this she ran out of money quick. My sisters landlord let her stay rent free for 3 months on the promise from my mom that she would find money somewhere. My mother is broke and lives month to month on social security and my other siblings cannot afford to help at all so this was never going to happen. The landlord lost his patience and now is demanding payment to the tune of 6k (4 months rent plus money she owed him from a loan) or her will be locking the apartment and taking her to court.

This is where I come in. Last week my mom called me up and begged me to help. I am much better off financially than the rest of my family. I can afford to give what the landlord is asking for. So I talked to my sister for over an hour as she apologized and begged me to help her. Both my mom and my sister told me that this was a "loan", and once my sister was back on her feet she would pay me back. After an hour I stopped her and told her that I don't believe her one bit on paying me back and I'm not gonna bail her out of the situation she got herself into. She already owes me and I would not help her. I hung up and have ignored her since.

My family is furious at me. They have been calling me nonstop all week trying to get me to reconsider through shamming me and telling me that I am being petty. My mom has begged me to at least buy her a plane ticket home but I won't do even that. I don't care if she lives on the streets. She decided to move out there and got herself fired. She had months to come back and stayed. It's not my problem. Everyone else says that I'm being supper hard. My mother has even offered me her house (once she dies) to help repay me but I still refuse to help.

Am I being unreasonable here?

Edit:

Since people are asking and I wasn't clear enough. My niece lives with her father. He has custody of her. Its a long story why she lost custody (and involves why she would be turned away at a shelter). I'm not comfortable sharing more than that. She moved there originally when her and her ex got back together and to be with her daughter.