@Spoonikle
ah, the acting more childish thing, yeah that's definitely happening. part of it has to do with being in a more secure environment (the university). when you aren't in constant danger of being murdered by bandits/fanatics/racists or eaten by monsters, your brain relaxes a bit. she was FORCED to act as an adult too early (even if she was technically an adult when she left her village), and now that she's actually somewhere safe, you get to see her react to more minor problems like these, which she generally DOES respond childishly to. Even later in the novel, roxy acts like a kid when she's being spoiled.
here, she's not being the A-rank adventurer who had her party wiped out, she's being the new student from the demon/magic continent.
so yeah, you're totally right, she's acting a LOT more childish/child-like in this chapter
it IS before rudy, though. After she teaches rudy, she works for the shirone kingdom as the court mage. one of the reasons she got hired despite being a demon/magic race in a family with a Milis believer is because she was a university graduate.
she gets her Water magic rank certified at the university (Water King, iirc, since Rudy uses Saint rank for his 'graduation') and is already certified before she meets rudy