Audrey, I'm sorry to hear this...Why did your sister even GET a dog? It sounds like she doesn't have the desire or the responsibility to care for the dog and that she just wants to enjoy the "glory" of saying that she has one...? I know she is older than you but it sounds as if SHE looks up to YOU.
I have a crate, a VERY large one that I will happily mail to you for your sister to use if she can't afford a bigger one...the thing weighs 50lbs easily and will probably cost more to mail than it would to buy a new one...LOL! But I will do it for Jade's sake...
I think Giselle's advice was great and I don't have much more to add...It bothers me on personal level because I adore you and hate to think of you being upset about your sister's irresponsible behavior towards her animals, and I think, the rest of her life....
What does your father think of you getting another dog? Would he be OK with Jade living with you? That's alot of dog in one house...Perhaps you could arrange something with your sister where you train Jade for her a few days a week (she would have to be there too of course...) and you could show her first hand that the problem is not the dog....train both of them at the same time actually.. I don't know darling....I wish I could help more...If you need the crate mailed, let me know....Love ya!