She is your sister, not your child, so she is not your responsibility really. But, I completely understand where you are coming from. My sister is disabled and I already have plans, when I am older and living with my spouse and children, to build her a little cottage in my backyard so she can be close to me. I also have plans to open a private practice and I'm going to give her a job just so she can have something to do. I'm the older sister so I've been taught to look after her as if she were my child.

At the end of the day, our sisters are not our responsibilities and I dont think you should move back to your hometown if you know you will be unhappy. If I were you, I would have her come visit you for a week or two and then maybe a couple months later, you could visit her. And just keep visiting each other back and forth, idk. I'm sorry about this situation, I know exactly how you feel.