You don't, at least not in that way. You can
explain that this is a fantasy film, in much the same way as "Revenge of the Nerds" was. No real-life professor at a secular college could get away with making the students sign those pledges. It would be an enormous, nationwide shitstorm (you might want to use milder language) because it would be on the interwebs five minutes later. The professor would be disciplined tout suite, if not fired (presumably he's got tenure.)
Professors at religious schools can
get away with similar things in the other direction, because that's what you signed up for.
And naturally, given the type of fantasy film this is, our hero's clever arguments meet with only the feeblest strawman resistance, instead of the strong reasoned responses they'd get in real life.
And when the guest celebrities get asked questions by reporters in the movie, it's always the softball, easy to slam dunk ones, not the ones that would be difficult to answer or where the answers might not please the Christian audience. (Mind you, celebrity interviewers asking softball questions is pretty true to life. It's not like they're being grilled by Mike Wallace or anything.)
So as long as she goes in knowing it's a fantasy film, just like my fanfic where I defeat the big villain, get the girl and am crowned Emperor of the Multiverse, she'll be fine.