Katie & Trev

Your fiance is seeing how easy you are to manipulate. This won't be the only example.
You are in what researchers call the "evaluation phase" of this manipulator, where they try different tactics on you to see what works. If they see that they can bait you and then withold the information to keep themselves in power over you then it will be played again and a gain in a thousand different configurations.
Nobody knows better than the manipulator that what they are doing is mean and stressful. But they put on this act, pretending their motivations are good. The purpose of doing this is to see if they can get away with saying the opposite of what they are doing. Naiive, gullible, and super-conscientious people will listen to their smiling lies instead of watching their nasty actions.
The literature says this: first, pay attention to your gut instincts: your gut says something is wrong, which is why you posted. You're darn tootin' something is wrong: you're being manipulated. Look very carefully for where else your gut was saying "red flag". Did you let them explain them away?
Second, it says to cut manipulative people out of your life instead of suffering the insufferable. Manipulative people make for horrific marriages.
Third, if you have to live with one because it is family or a work co-hort or whatever, they say to give them choices - and these choices have to be enforceable. I don't know the specifics in your case but if this was someone new to me I would say to them that they either tell me or else this is the end of our acquaintance: I don't put up with manipulative #######. If this is some kind of outlier (which I doubt), then a similar choice is to tell them that this is the end of any conversations with them until they tell the truth. You cannot let people pull this on you or there's no end to it.
If they are cruel and unreasonable they will say they are sorry they brought it up and blame you for pressing them: then you know you have a real nasty one on your hands. A nice person is going to apologize immediatly because they have empathy for you, and tell you. The cruel person starts with a mean trick like this and then ends up blaming you for it. That isn't love. It's a war. That is how a manipulator views relationships: A war for power and control, but played in dirty underhanded tactics instead of being honest and open about it. Because underneath this mask is coward who works by deception instead of open and above-board.
There will be people saying I am reading too much into this, but they aren't the ones who have to live with a person that does this to you. If you like how you feel now, then just multiply by a thousand to understand what a life with them is going to be like if they are pulling this kind of ####### on you.

I met my fiance on World of Warcraft too !

I'd tell him you'll mail the Green Card after he repays you for the debts you incurred on his behalf. After he pays you back, mail the Green Card, but to USCIS.

I met my fiancé online (On WoW) in late 2008 sometime, I can't really remember. Might've been September, and we were really close friends before deciding to make things 'official' and started dating July 29, 2009 - We had feelings for each other way before that, but he'd been in a long distance thing before (She lived in another state, so it wasn't super long distance. It didn't work out 'cos she cheated on him), and I hadn't, so we talked it over for a while. I flew out there to visit him in November 2010 (3rd-17th) and he proposed to me on the 14th and all his family came over We didn't take any photos of the dinner though (Had it at his grandparents) 'cos I'd got a nasty cold (Flying from Australian Summer to the middle of Ohio where it was cooold!) and passed it onto my fiancé, so we had dinner and said our goodbyes and went to bed! Lol.
gosh I wrote an essay... Lol

I think everyone else has pretty much said what I was going to.
I suggest you run. Fast. Do everything you can to stop her coming to America to stop her taking advantage of you further, because she WILL. She sounds like she doesn't love you and just loves your money. Call the embassy and NVC and tell them you -refuse- to marry this woman, if she already has the visa in her hand. Don't marry her, then she can't stay and take advantage of you!!!
You're being taken advantage of, and emotionally blackmailed, and in the long run, she -will- destroy you financially, and probably mentally too!
I know it's gonna' be hard for you to read this, and what everyone else has said, but if so many people here at VJ can see it, it's obvious that alarm bells are ringing - and they should be for you too.
Good luck with everything. You are NOT cheap, you sound like a really good, nice guy, who is being taken advantage of. Keep us updated.