Even if she is 2 years behind her original classmates, she can just make new ones. Here in the US most kids don’t go to college with a group of kids they’ve been with for a decade. If the student goes to a state flagship, they may know 10-20 other kids, and may know some older and younger kids from the same school, but most make new friends. Even if they do go to school with a group from high school they may drift apart in college because of different majors, different interest, meeting new friends (especially a romantic partner).
I think what the other poster was saying is that if she stays here in the US she won’t go to school with those childhood Brazilian friends, and if she goes back to Brazil and is two years behind them she still won’t be in that old gang. So what? She’ll go to school and meet new friends. In no scenario will she be with them again. That decision was made a long time ago and you just have to go on from here.