I do not think you need a "green card" just to enter the USA. I have a number of friends that work for the cruiselines that often come in and leave the country with just their passports. Now in order to STAY in the USA they need some sort of card or visa or deferment paper that is good for 6 months or a year. If your friends passport has the entry stamp longer than the time allowed without a visa or deferment then she does need something else I believe. The very best thing to do is to have her go or call the immigration folks and get the infromation first-hand from them explaining why she needs this info and what she is doing etc. Much too important to just rely on what we say here. All we can do here is tell you what "we" have seen or experianced in the past.