This is a sad story. It sounds like these two are better get divorced. In such case, even children are better off if the parents divorce than if they stay together. Although I don't know them personally, I am sensing here that the situation is much much more complex than it seems it is. My observations are based on verious situations that some of my friends had to go through.
(1) Did she love him when they were living together?
Yes, she did.
(2) Did he cheat on her when they were living together?
Yes, he did.
A few years ago, her husband sent her U.S. to study. Now, she has college degree, a professional job, and U.S. legal status. Also, she has a new boyfriend (happened to be another nepali guy) and lives with her bf in neighbouring city along with her younger son. Currently, her husband is in U.S. too living with their elder son. I guess her husband still wants to apply for U.S. legal status being her spouse and some money along the way.

If you are a married woman then think about following:
1. What do you think if your husband cheat on you?
2. What do you do if your mother-in-law along with others don't like you and you don't have any choice? It's like living in a ghost house where everyone around you is your enemy.

If you are a married man then think about following:
1. What do you think if you send your wife to study aboard and later find her with someone else when you come to see her? (may be she is taking a revenge for what you and your family did to her, may be you are no longer handsome, may be her new bf has U.S. degree and you don't, may be her bf has longer than yours (:, may be all of the above).
2. What do you think if your wife (still not divorced ) stay with another guy and with his suggestions, she blames you and your family?
3. What do you think if you spend time and money for her and later she leaves you because she is now in better position and sees better career with other guy?

People, if you know them personally, let me know where my observations differ.