She is asking far too much of you. Yes, you are family, but that does not mean that you owe her a living. She has no reason or motivation to find an apartment or a job if she knows that she has you to pay her way for her.

If you stop giving in to her, she will move on to someone else who will pay her bills or she will start to take her situation seriously. You can support her by helping her apply for housing without giving her any money to pay her bills.

You are not abandoning her when you are taking care of her own family. If she wants to say that family is required to help family, why doesn't she list out all she has done to help your family? Does she babysit? Does she come cook and clean for you while you are busy taking care of your kids or at work or whatever?

She is being ridiculous and she knows it - she is bullying you into giving her what she wants. She'll say whatever works.