Interviews really serve as PR for the school rather than as a way to screen applicants (beyond picking up on an occasional red flag that may not be evident by the application). There is no reason to think that the interviewers would have a basis for decisions making. But a very strong prospective student who connects with the interviewer will probably be more likely to consider the school seriously. Also, it keeps the alumnae connected to the school and feeling some ownership/commitment to it.