It it’s of any ethos, I was going to go to Emerson College, but decided against it. Film is very interdisciplinary, but depending on the kind of film school she’s interested in applying to, that will be less the case.
For example, if she’s applying to a liberal arts school like Wesleyan, her overall academics will matter more than a single film class, but specialized institutions like UNCSA might look at it differently.
If she’s more interested in the former, so long as she has solid grades in humanities or social science classes, her B in film wouldn’t be much of an issue. English grades are very important. If it’s the latter, see if her high school advisers are willing to let her challenge the grade she received. Since she won a competition, there is at the very least an argument for it.