How can I prove my wife only married me to get a green card?

My wife is from Ecuador, and we married a little over a year ago. I had feelings my wife was not in this marriage only for me and she proved that last month by going to a women's shelter in order to protect the issue of her permanent residence card. She is claiming all of the things these web sites and friends taught her to do, like Gross Neglect and Extreme Cruelty, all in an attempt to obtain her permanent staus through any means possible. She also now claims she did not understand the prenuptial agreement we both signed and had notorized. Two weeks before our 90 days were up in our fiancee visa, I had asked her to please return to her country, because I felt we needed more time. She responded by saying that if she returns to her country, she wouldn't return here. Do you feel based on these two displays of dishonesty, I have any chance to have this marriage annulled. I am very worried now about this person. She is in Minnesota now with her cousins and receiving more advice on how to manipulate me and the system. I risked my own independence by retiring early to help her only to be beaten down with false accusations in order to protect her Permanent Residence Cards. I am trying to prove fraud and I need all of the help and advice I can get.