I think she should pick the college that is the best fit academically/socially/financially and once she is there she can look into the selection process to become a RA at the school she is at. Because it generally comes with free dorm room (although the RA can’t usually choose the dorm they are assigned to) , the process to become a RA is typically highly selective so it would be silly to go to pick a school that is not the best available fit for a slightly better shot at being a RA. Once at a college, she can learn about the time commitments and responsibilities (which are significant) and make a rational decision as to if it would work for her. There is no chance of being an RA prior to soph. year so it is too early to worry about it.