I'm not talking about the brainwashing ability that comes with the Lust skill. Some of the characters comment that Ms. Oka can't be reasoned with because she fully bought into all the "crap" the elves told her. So, is that the case? Is she like Yuri? Indoctrinated at a young age with with the elves taught?
It's actually a little more complicated than it first seems. Because first of all, it's stated in the light novels that Ms. Oka and Potimas (the leader of the elves) don't actually trust each other. The novels state multiple times they are both merely using each other for mutual benefit. And this relationship starts when Ms. Oka is still a newborn, and gets the telepathy skill so she can talk to Potimas and try and save her students, who she knows are endangered because of her Class Roster skill.
Her distrust of Potimas is apparent on page 85 of volume 5:
I have no doubt that Potimas would be willing to purge me without even the slightest change in expression.
Even more importantly, that might endanger my students who are in the elves' care.
The elves are not protecting them out of goodwill, after all.
What the elves teach Ms. Oka is that skills are bad because their acquisition helps power up evil beings called Administrators. Gaining a large number of skills will put you on their radar, and they'll take all your power for themselves. This is why Ms. Oka advises Shun not to raise his skills too much.
Now, it seems apparent Ms. Oka did buy into what the elves taught to a large degree. But what makes this complicated is that her Class Roster skill actually seems to confirm what the elves taught her. The information from Class Record is actually very limited, giving information on Past, Present, and Future. (see pages 80-81 of volume 5). Present just gives a one-word description of condition, past tells where they were born, and future tells the manner in which they will die in one sentence, and a rough estimate of when. It's future that is important here.
From page 84 of volume 5:
If such a reincarnation was to acquire and strengthen a lot of skills, then according to the elves, they might catch the eyes of the administrators and be exploited for their purposes.
I have good reason to believe this story.
One of the causes of death listed in my Student Roster is "divested of skills."
Even now, it's still listed as the cause for Shun and Katia, among others.
Initially, most of my students were fated to die for this reason.
I suspect this would indicate death brought about by an administrator.
Now that many of my students are in the elf village in an environment where they can't improve their skills, the number of skill-related deaths on my list has decreased.
Thus, while the elves may be misleading her, and even if she suspects as much, Ms. Oka has good reason to believe that what they're telling her is mostly true. And since she's using her best reasoning here with what information she has, it's hard to say she's actually brainwashed.