first off she needs to oficially change her status to single that should be done by taking care of divorce papers... then i would advice you to get the marriage certificate as soon as possible go to the county office or court and get married. And have the certificate.. Wait till she becomes citizen.This way you would get you greencard within a year and by this way your process would be easier. YOu can apply now but it would take another 5 years for you to green card. And the way the way you talk i feel that you are not going to hang around with her for too long if your intention to be with her was just to get green card then i would suggest move on or wait till she becomes a citizen... Anyway its your life and im not a personal counselor nor an immigrant expert.. its just my thought, you should consult a lawyer.. good luck