Will she be able to get legal guardianship over her 18 year old sister with Asperger's Syndrome?

Her sister Jane lives with her but can't take care of herself. Jane needs to address her mental issues and refuses to. She won't get a job. She posts obscene photos of herself online and chats with men in an unacceptable way and then goes out to meet them. Will she be able to get legal guardianship over her 18 year old sister with Asperger's Syndrome based on these factors?