Thanks for the chapter!
Looks like all those Lamia she fought had an effect on her evolution. Although isn't an arachne suppose to have the human part of the body replace at least the upper part of the spider's head rather than sticking out the top of it? She'll probably be able to change back to fully human form again as MC wouldn't be able to sleep with her otherwise. After all, not enough of her human form much less space between it and spider head for him to do her like that and MC probably doesn't know enough biology to even have an idea where a spider's naught bits are much less if he's compatible with them. Be interesting to see what she does with all the webs spread around the arena.