So I'm a Spider, So What? - Kumo Desu ga, Nani ka?

[DarthEnderX]

I think they needed to do a better job of illustrating that plenty of time had passed,

Yeah, cause the spider segments kinda give the impression that the whole thing was taking place over, maybe, a day?

But then you get to her other classmates, and it's obvious they've been in their bodies for awhile now.

I mean, she awakens poison/acid immunity the moment she gets hit LOL. That's kinda op.

I agree. Though if that's normal for the world, then it's technically not OP as anyone can do it.