I'd say shaq at this point, she doesn't have the reach or the strength, once it gets into a clinch shaq should be able to win..
Rousey can win if she boxes more in and out and dance around and she can win.
So it really goes down to the style of fighting, if it's grappling, she's not going to win, if she can box 1-2 punch and in and out, she has a chance, it doesn't take a lot of power to hit the soft parts of the body even 7 footers will go down on.