my wife is chinese born but has been a US citisen for 5 years. can she get a 180 visa?

She has traveled to china on her US passport 3 years ago with a multiple entry visa. Her parents are deceased but she has a brother and sister who live in china and are Chinese citizens. She is planning a trip to china in April and would like to stay 5 moths. How difficult would it be to get it and how do we do it?