If you go to canada to renew your visa US embassy in canada has rights to ask you to go to Nepal (your country of origin) to renew your visa. As long as you are going to school and taking full load of credit i.e 12 hrs/semester for undergrad and 9 credit for grad your visa is automatically renewed...Hope that helps..but in her case you didn't mention that reason for visa denial. what was the reason to reject her visa  and how was her financial status...did she had GA or TA or enough bank balance to prove that she can pay her own tution fee?