One of my friends has gone through this process, His Fiance is from Thailand. He started the immigration process in late februrary and she came in the US in late June. It took them only 4 months to tie the knot. But if you are thinking of applying her/him as US citizen's spouce then the case is different. At that case, she/he can't come here in US as a visitor the only option is as an imigrant.which normally takes longer than the Fiance Visa process. good-Luck