I think she outclasses him as badly in grappling as he outclasses her in striking. I think it's a tough call.
Remember when the entire MMA world was convinced that the better grappler beats the better striker 100% of the time? Ah the good ole days. I'm glad people are appreciating striking for what it's really worth, but when you're talking about the most extreme version of striker vs. grappler, and especially where the grappler is an actual MMA'ist, I find it hard to pick against the grappler.
Obviously Floyd being... oh, what's the word? Oh yeah, a guy, that makes a huge difference. So it's like a too many X factors to say kind of thing. But despite the gender difference, I still think Ronda can ragdoll and armbar him before he knows what's happening. It'd just be hard for her to get through the punches.