its too late now. very much irresponsible on her part too (he is obviously guilty ). ever heard of family planning ? this is 2015 and USA we are talking about.
having said that, its not end of life for her as it used to be in Nepal. this is USA. he is required to pay child support (seems like he makes good money). and its OK for many prospective husbands if she has a child provided she is a really nice girl. so first order of business is to tell him to make a decision. he has to choose between his wife and girlfriend. this has to be decided sooner or later. sooner the better. its already a messy situation, don't complicate it more. and no he cant have both, huncha ni nepal ma dera ma keti rakhne, gharwali and baharwali. this is USA. it wont work and will only make things worse. don't waste the wife's and GF's valuable time (age). if he decides now, they will have more time to find their true life partner.