From what you have shared, you have done everything right, so I agree with others that the probability of approval is high. The previous two K-1 denials may have had something to do with the interviews, maybe her answers were not believable to the officer. Having a sister and aunt in the USA was likely a red flag. I suggest that you help your wife to prepare for the upcoming interview so that if she is asked about her family in the USA, she has an answer that is more focused on you and your marriage relationship. She should know everything about you--past marriages (if any), your children (if any), all of your details including date of birth, place of birth, where you live and have lived in the past, your profession, where you plan on living together, her plans for work, education, starting a family with you, etc. Practice with her to make sure that she answers with confidence, and that her reason for wanting to live in the USA is to be with you. Sometimes people get nervous in the interview and the officer interprets this as not being truthful. Good luck!