My sister is so rude and wants me to pay for her University?

I am 33 and my sister is 27. She is just so rude and unbelievable. Her whole adult life I have tried helping her financially. I've loaned her money that's she's never repaid. I've co-signed on an apartment for her and she moved out leaving me to pay for it. I let her live in my house when her and her daughter had nowhere to go. This is just a few things I've done for her. Yet she is so rude and just hateful. She has a 3 year old daughter that was the only child in the family. Last year when I found out I was pregnant she just started to say and do mean and hateful things to me. Right around Christmas she did something that I don't think I can ever forgive her for. My husband and I are going through a rough time financially. He got into a bad car accident that has left him unable to work. He has kids from a previous marriage that he has always paid for. However since his accident we can't afford to pay all the support until he gets his settlement check.His ex understands. The state does not. There is a bench warrant for his arrest. My sister wanted the whole family at her new place for Christmas (not really her place but the guy she's seeing). She said my husband was not welcome. If he shows up she will have him arrested. I was and I am still am very angry. Just 2 weeks before she let my husband watch her kid while we went Christmas shopping! I just stopped talking to her. Now my daughters 1st b-day is in 4 days & I wanted my niece to come to her party but my sister refuses to let her come. My niece loves her cousin and my sister just isn't being fair to her. The crazy thing is that my husband & I did nothing to her and she's acting like we screwed her over somehow. Why would she be this way? She has always been the baby of the family and now I think she wants her daughter to also be the baby. She has always been immature and now her immaturity has turned to a hatred jealousy and I think it's because my daughter is now the baby in the family. What do you think?