This is from my experience ( Now it might be different) To enter in US, she needs to have her F-2 visa in her passport. She needs to go through the application process again. She needs to apply for F-2 visa in american embassy. She needs to have her dependent I-20 and your financial support documents again. As you were suggested before, I suggest you to talk to your international advisor. S/he is the one who knows the best. Good-Luck