A co-owner is asking if their sister can legally sell her portion of a jointly inherited property without the consent of the other co-owners, especially since the property hasn't been formally divided and she only has a WhatsApp copy of the will. The original property papers are with the enquirer. Legal advice suggests that while a co-owner can sell their undivided share if they have proper documentation, selling without proper partition or consent might be illegal. It's recommended to challenge the sale in court if it's deemed invalid and to seek professional legal advice with the original will documents.