The lore directly doesn’t mention Arachne being half-spider and half-human. But there are quite a few renditions of her in that form. I like the idea because it would be really cool and fun to sculpt such a creature, but also because it would be challenging and skillful to retopo, rig and animate (and it would be pretty awesome to see as well).
Because there are many interpretations of Arachne (some where she only has a human face and a spider’s body, some where she is just a giant spider; but mostly she appears as half-spider half-woman), I have to ask, will this critter suffice? I hope she fits the bill for a mythological creature?