Hopefully someone with first hand knowledge will chime in, but my next door neighboe was accepted to USC for film. His parents are art professors at another college and had a connection, so they knew where he stood through out the process. Once he cleared the first cut by admissions (grades, scores, etc) the film school looked at his app. After that stage they took the “finalists” and looked at their portfolios in greater detail.
I think as long as the general application and portfolio is strong enough the B in film won’t be that big of a deal.
The bigger issue is she will need multiple recommendation letters. Do you think this teacher would write her a glowing rec?