Looks like I was indeed too hasty to judge Lefiya to be completely changed. She's still the same old cute and goofy Lefiya under the hood, she's just much better at concentrating on training and fighting now. Of course that obsession with getting stronger, with actually valid methods to achieve it, will make her behave differently much of the time. But that's largely due to much of her time being spent on activities where her personality doesn't really matter that much, such as fighting and meditating, even dungeon exploration. But whenever she actually interacted with people outside of those activities, she was still the same. Though I'm sure Ais was pretty shocked. Ais herself isn't really capable of higher brain functionality what comes to human interactions (or elven interactions, whatever), so it can't be helped.
Pretty shocking bits of info dropped in this chapter when I'm hopelessly behind on anything that happened in the main series.