Does she renew her green card and then we get married and then what do we have to do?

Although not clear from your question, it sounds like your fiance is a U.S. Lawful Permanent Resident (holder of a "Green Card") and you are interested in the possibility of her sponsoring you in an immigration application after you become married. If that is accurate, then significantly more information is needed in order to advise about the steps to be considered and taken. Generally, a Permanent Resident may both apply to renew her Green Card and sponsor a spouse in an immigration application. Additionally, a Permanent Resident whose "Green Card" is about to expire may be eligible to apply to become a naturalized U.S. citizen and then sponsor a spouse for immigration benefits in the Immediate Relative visa category (which has multiple advantages over sponsoring a spouse in one of the "preference categories"). It would be wise for you and your fiance to consult with an immigration attorney who, after learning all of the relevant information, could advise about immigration eligibilities, options and strategies, and who then could offer legal representation in the often quite complex application process(es). Some immigration law firms, including mine, offer legal services on a "flat fee" basis so that a client will know the total expense from the very beginning, and a few immigration law firms, including mine, offer an initial consultation free of charge.