@Kaitensatsuma
Why not?
Most people choose they do in college based on their grades (at least in east asian countries like Korea and Japan). It truly has very little to do with what you want to do for most people. If you have good grades, you get to go to law or medical. If not, you go for places like Humanities. Plus, as far as I can tell she doesn't actually have machining nor engineering experience( the most she's likely done is disassemble and reassemble hundreds of gun models)- and she doesn't need any, since she can learn blacksmithing combined with magic, as long as she knows how they function and a basic blueprint.
ie., she's a normal student with average grades who happens to be obsessed with guns. That's far more reasonable, and frankly, would be more likely than one might think.
Also,
Blyat