@Kampfarsch
Going by the fact that it took 30 chapters to end volume 3 and Arachne evolution happens at almost the end of volume 5 then:
Volume 4: 30 chapters
Volume 5: (until Arachne): 25 chapters
Volume 4 + Volume 5 = 55 chapters.
If mangaka-kun still being lazy (1 chapter per month):
55/12 = 4 years and half.
And this is if he still doesn't adapt the Side Chapters which are already important by the time Kumoko reach Arachne.
We have had chapter 1 and an interlude of Volume 4 (LN) in this chapter and that happens near the end of volume 5 so I'd say between 15-20 chapters, so it's still likely gonna take atleast a year til we see it in manga you could always check pixiv
@JWChibi 'Cause her mom was messing with her will first, making her dislike dragons and stuff like that, general influencing. I think for lower power spiders the mom just mind controls them straight up, too.
I don't remember if it still effects her now or only when she was lower level, but either way she took it personally and was like "I should get rid of mom so mom can't influence me". If she is still vulnerable on some level, then she wouldn't be safe even on the surface anyways.