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First of all: B2 is a tourist visa for short stay to max 6 month under I-94, secondly you can't over stay in any condition more then 6 months as per I-94 given by border control officer ,you can't work , you can't be employed , then finally you can't get married to an American citizen forget about  her friend who is on F1 visa ( it's just study visa which is also a non immigrant visa ) so technically both can't get married , first her friend Has to to finishes F1 study , he has to find a H1B sponsor employer then if all goes ok then otherwise he will have to come back himself if he doesn't he himself will be illegals in USA , so let's suppose he find an employer then he has to apply for spouse dependent visa that is only possible if they are already married otherwise not , so he has to first come to India get married and go back alone and apply for her spouse dependent visa under H1b category for spouse dependent ( she can't work in that) and in between she can't travel on B2, she can't even apply for B 2 , the processing time for spouse visa is around 12 to 18 months. Who ever suggested her to apply for B1/B2 visa is super foolish , well now the situation is worse cos she is already been refused once the chance for reapplying and getting visa is next to nil , I would say zero percent. Don't reapply , wait for her fiance to finish the studies and then apply for H1b sponsor, if he gets it , come back get married and go back apply for her spouse dependent visa under H1b sub category, there is absolutely no other way. Don't waste your money with agents or training programs. Or coaching classes , she can go to use but it will be a wait game and he has to get an employement, so let's say 3 years from now she can  be in usa.