It's better to have them before leaving. Most of them can be applied on net.
If there is any document miss and already in US, then have to ask family in Taiwan to take care for you that maybe lots of trouble for them.
Important: There will be a lot of paperworks in INS so her fiance has to ask about all the detail such as what kinds of document she has to provide and what kinds of application form they have to submit and how much he gonna pay for the application before she goes to US. They have to get all the document done before they apply; otherwise, INS may reject his application in any reasons.
Hi Shayna, Which state are you right now? I suggest you email me, then I can tell you more detail. There are a lot of things have to explain.
If you want to be an American, then I strongly suggest you to stay here and get married asap.
to 史小妹, After your friend's sister got married here, then doesn't have to worry about ticket stuff. Only thing is she has to give up the ticket and waste some $. I suggest not go with travel agent because they have many restrictions. Only you 2 come together will be fine. I came alone and told immigration officer my friend invited me to visit her that's all and I still passed. However, her marriage certificate and INS application has to be done before authorized stay expired.