My Colombian boyfriend (with Argentine DNI) was quaking in his boots when he applied for the U.S. tourist visa. Young, old, rich, poor, they're are always treated like drug mules no matter which country they're trying to go to. Hell, even I got thrown in a room to wait for a full body scan leaving Colombia because I was a young woman traveling alone with a ton of stamps showing years of travel between Argentina, Uruguay and Brazil, and I told security I had been traveling around with my boyfriend. (That was the wrong thing to say, even if it was the truth). It's just the way it is. Sad but true. He had been in Argentina working legally for three years when he applied for the tourist visa, with the same job he'd come to Argentina for. He had all the bank statements and everything, and got the visa, because he was able to prove that he'd go back. His Colombian friends who had visited the U.S. before advised him to not even mention who he was visiting or why, lest they think he was trying to stay in the country. I think he told them he wanted to visit NASA or something.
I am sad to say that I'm not in the least bit surprised that your wife was not granted a tourist visa. I am a little surprised that you thought she'd get it, actually. Because no, marriage does not make a difference. She had nothing to show that she was tied to living in Argentina. If anything, the fact that you were supporting her and paying rent and her sister's tuition might have just made her look like an opportunist. And earlier you said that she did everything 100% legal to immigrate to and have a life in Argentina. Well, if she was working en negro, that's not entirely true. Because now, unfortunately, she doesn't have the years of work records to prove her case. Her only roots in Argentina are financed by you, her American husband. I don't think it matters whether you plan to stay in Argentina or not, since they have told you that the two of you being married makes no difference in her application. I wonder if showing your financial status did more harm than good, I guess is my point. As unfair and unkind as it may be, the two of you are going to get a lot of skepticism thrown at you from the officials due to the fact that she's young, poor and a Paraguayan immigrant, and you're older, considerably wealthier and American. If you were a government official who'd seen it all, what would you think? It does not look good on paper, and that's all they care about. They think she's gonna drop you like a hot potato as soon as she lands, to put it bluntly. It would not be the first time in the history of U.S. immigration, that's for sure. I do not say this to be unkind; I say it to stress that you should not view your marriage as an asset to her case here. They seem to have made that pretty clear.
I sincerely hope that you are able to resolve things somehow, so that she can travel to the U.S. and meet your family. Get going with her monotributista stuff, stat. Good luck!