While it would be nice to help her in every way possible, you're doing just fine by being a wonderful sister to her.

"The City" as it's called is far from normal even by other worlds standards as far as I've seen, so you give her a reason to believe there is something more for her out there than that life.

Of course, if you do want to know more about magic I could teach you, but it would be a long time before you're ready to deal with such theoretical things as crossing worlds. Even I will have to lean on the knowledge of people far older and more powerful than myself.