Would Marilyn vos Savant be proportionally more likely to take over the world, if she tried to, than a 115 IQ individual?

Sure. She's demonstrated that she can communicate successfully with millions and handle her own affairs quite successfully, generally winning at life. This is comparable to, say, Ronald Reagan's qualifications. I'd be quite unworried in asserting she'd be more likely to take over the world than a baseline 115 person.