I would like my Sister(in her 40s) and her daughter(unmarried and completing graduation soon) to visit us in US for a family event. She is married and her husband has his business back in India and her son (unmarried) but working for a tech company. They are staying in a rented apartment and have couple of properties in her name. What are her chances of getting a visitor visa? Secondly, do I need to send any documents (e.g. bank statements, letter etc) that is required for Visa application?