Fiance Visa - K1/ K2/ K3/ K4

i met my fiancee in 2004 when my mum and my sister sent some gifts through her aand her mother,but then i was married.but i lost my child and my wife in an acident in 2006.then my my friend who is now my fiancee heard about this and felt sorry for me.we started the affair since december 2006 and she came back to nigeria in 2007 when her father was killed by armed robbers.we decided to get married and she filled for me.i was denied visa on 16th of sept 2008.she now want to file petition.is it advisable for her to do so or she should come to nigeria so that we do court wedding and file 4 spouse visa.cos she is so afraid that she might be killed as they killed her dad when he came to nigeria. i took the pictures taking together and the one she took with my mum when she traveled to usa and also the one taking by her mum,my mum,her late dad and my sister.i also went there with evidence of our chating.i also showed the dead certificate of my late wife.i have a well paid job,i dont know why they like denying ppl of their happines.my fiance is a citizen of america and yet they dont grant her her happines.then how are we going to leave together.