Based on how they found each other and her lack of reaction/understanding of things, she seems to be the complete antithesis of what a stereotypical Jorogumo is supposed to be, IE very manipulative literal man eater who will lure an unsuspecting victim with the false promise of love and affection.
(I mean she could be faking it, but I kinda doubt that). Her being in this state of blissful ignorance about the state of being of Jorogumo in general will work to everyone's advantage as all our characters can lovingly mold her into a person who able to learn about being more human and how to interact with the world around her.
Something that won't leave my brain is that granny Kawashima is probably the youngest of the three going shopping. We know Kogane is many decades old, and Yotsuyu doesn't even know how long she's been alive. It also sets up a nice progression that the youngest of the three is the most mature, and the oldest is the least mature.
I'm glad Goro realized that he and Kogane were living in the glassest house criticizing Toda and Yotsuyu.
We're gonna have to wait until Yotsuyu develops an interest in Toda before anything happens on that front, lads. Buckle up. it's gonna be a long ride.
Also, Yotsuyu's "extra" arms creep me out. Not a deal-breaking, but I don't like looking at them.