Sadvi,

I have seen the same case happen to some of my friends here. In your sister's case, like people have suggested above she needs to mainly convince the consular that she would return back to Nepal after she's done with her studies. It is up to you and her what to think of and say to consular to make him/her believe that. Some examples might be your parents are alone in Nepal and you having the green card would not return to Nepal to take care of them, it has to be your suster after she finishes her studies; her engagement; some property in her name etc, anything that might show the chance of your sister going back to Nepal after her studies; job offer might not be a very good idea because think-it is hard for companies to offer job to someone who would finish education and return after 5-6 years, companies will find many within such a period of time.

Choosing major-at least for now-that matches her +2 major or stating major studies as something that does not have a very good scope here in the US and is mainly utilized in countries like Nepal, for example sociology or rural development or something like this.

Another main thing is I have seen several people say that upon being denied a visa, if they politely but firmly ask the consular the reason for their denial, and again try to convince him/her that they (applicant) would return back after the education or visit is completed, they have been given visas. But the applicant should be firm or even politely argue with the consular to prove his/her point.

Good Luck to you sister!