For get about taking to court

You have no chance to win, based on the Affidavit-of-Support you signed.

The best defence you could have is to to hide all your cash, and negotiate with the girl. Give her two choices. Either you declare personal bankrupcy and she will be kicked out of the country bacause of lacking of financial support; or you paid her a lum sum of money in exchange for her agreement to abstain from pursuing you legally.