Easy, Your aquientaces didn't do any research is their fault. There is this one form called Adjustment of status that you can use to stay in
USA when you marry a citizen. If that does not work legally divorce and have the person leave the country and apply for a
fiance visa Then you can marry and do the adjustment again.
To bring a family member, friend or whoever as a visitor a citizen resident you need to fill out an
affidavit of support I have even brought people from cuba this way to come and visit me. Bringing Cuban visitors is good, they are legally allowed to bring cigars and rum.
I am not a lawyer but all the information is in the goverment site and all it requires is some reading.