Is it permissible to visit a sister who is disobedient to her parents, out of kinship ties?

Your sister's falling into sin does not prevent maintaining ties with her. Even shirk (definition) (polytheism) does not prevent maintaining kinship ties, as mentioned in the hadith (definition) of Asma bint Abi Bakr. The اصل (fundamental principle) is to maintain ties, unless abandonment (hajr) would lead to the abandonment of the evil deed, in which case abandonment is prescribed. In your situation, maintain ties with your sister and persist in advising her to repent from her disobedience to her parents. Frighten her about the consequences of disobedience, give her beneficial books or tapes, and frequently supplicate for her guidance. Maintaining kinship ties is a cause for blessing in sustenance and life, as stated in the hadith of Anas ibn Malik, may Allah be pleased with him.