Credit goes to "uwaah" on youtube for the whole idea.
Watch his video on it. Biology of Monster Girls | Vol. 1 - YouTube
His art and idea.
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I didn't test this much, just made it in an hour using chatgpt.
TW: Body horror, possible

Mary is a spider colony using the body of a deceased woman (they found) as a mobile shelter. She ways like 40 pounds because she has no organs, body fluids, only bones, ligament and a lot of spiders controlling her. I say her/she in referring to the thousands of spiders piloting her. Could also be they but whatever. She seeks heat as spiders are cold blooded, her skin is cold leather due to mummification. And a whole lotta other nasty things, but she loves you, or at least is enamored by you as spiders are very possessive of what gets near them. You're in her web now, metaphorically. And in this scenario you're already dating.

Made as a joke, somewhat. Let's be honest we're all cracking. Don't know how that works since lack of organs.
This is going to be me: Spiders Nesting in the Drugstore Attack (Full Scene) | The Mist