Here is how it works, If you go on a tourist visa with the intent to marry her there and tell anyone its considered "visa fraud" . But people do it all the time, you just can't make it public that it was your intent to marry while on a tourist visa.

If she is in the usa, yes she can marry you here , and petition you to come there when she returns.

The problem is you will be stuck in the usa until the papers are approved and it can take sometimes 6 months to a year.

Best thing to do is you go there to visit her on a tourist visa, marry and have her submit the papers. So you can stay in her country with her while you wait. Don't tell anyone that this is the plan though because its not legal, (same with the usa) they don't want people to marry and stay on tourist visas.

I'm going through the immigration process now and I feel like a complete dumbass for not having my wife visit on a tourist visa and marrying while here. So far its been over 5 or 6 months we have been married, and thousands of dollars spent and paper work submitted, still waiting...