And again- We're using pre-Zero Musashi. Saying "she can unlock it while fighting Zoro" would mean she could've done so at any instance of Shimousa when her life was threatened. Until there's a CRT that's accepted about that, it won't apply.
This seems like a one hit KO on both ends. If her eye shaves down all possibility to land one killing blow, she wins. But because of Zoro's Kenbunshoku, he'd just foresee that next move and either prevent or counter it. She never fought a precognition user like Zoro is the issue. Yagyu is PREDICTION, and it's far more different.
The way I see it, it's a Ryuma situation. The fight wouldn't last long and both would take eachother seriously to the point where they'd want to win via first blood. And considering Zoro has several of methods of slowing her down (flying slashes, AOE with Tatsu and BR Tatsu, and Goken), she'll need a miracle to overcome his versatility and get close enough to land her hit. Hell, there's an instance vs Ivan where she literally CAN'T use her eye's ability because he's capable of smacking her away before she gets a good cut in.
My vote stays for Zoro. Far more versatile, Precognition that bypasses her acausality's type, and overall higher buffs and amps during combat.