Kitteh Princess
The thing I'm wondering about the Arachne doll is how movable her arms will be, if she gets three on each side (I think that was the number)...
I've made a six-armed doll before.
xd
And I can tell you, it's not easy! I had to tear two Barbies apart to steal their arms. Then I had to drill holes in the doll's torso to make places to stick the new arms in and there's not really that much room there to stick them without them coming out of the doll's ribcage.
I think that the construction of the Arachne doll was much more simple. I think that she just has four additional arms attached to a small 'backpack' that clips with a peg into a hole in her back. So her body is the same as any other Monster High girl, except she'll have a hole in her back where the pack with the extra arms snaps in.
So I think her arms would have a great deal of movement since they wouldn't be constrained by her clothing or having to be stuck on her torso anywhere.