Hi. You are going to petition her through a marraige petition but she will not get her citizenship she will get her greencard. You will have to file forms I-130/I-485...(with some more forms) and these are filed through mail. You will have to determine if she is able to file these forms here in the US. How did she enter the US? This type of petition involves an interview. I would encourage that that you do seek the help of an immigration attorney...in order for the process to go smoothly. Good Luck!