We have helped you on this topic numerous times (with many options discussed) and I'm sorry things are still not working out for you all.
Unless someone is a danger to themselves or others, they cannot be forced or "convinced" to seek help. Because as far as your sister is concerned, she is always right. She doesn't believe anything is wrong with her at all. She thinks the problem is her family and everyone else. So in her mind - why should she be the one to seek help?
The only option as I have said before, is to change your living situations. If that cannot be done, there aren't any new solutions that we can think of, besides the ones we have discussed with you in previous posts.