I doubt you've even watched their fights. I'll lay it out for you.
1. Nunes has no cardio past the 1st round if she fights as she normally does, which is move straight ahead and throw bombs. It's been proved time and again. Against Valentina she was hesitant and mostly kept distance AND STILL GASSED OUT after 2 rounds.
2. Nunes doesn't have more power than Ronda. Ronda wobbled Holly with a right hand and forced Holly into a panic clinch. People gloss over that in favor of all the gifs of Ronda getting outclassed in the boxing department. Ronda can KO anybody in the division. Either fighter can turn the lights out on the other.
3. Nunes's style of aggressively moving forward, which she has done in every fight except the Valentina fight is tailor made for Ronda's style. Ronda would be happy to not have to chase Nunes around. Nunes is not effective as a counter puncher, unlike Holly. Nunes doesn't have Holly's footwork or flexibility to strike and move out of the way. Nunes is slow.
4. Nunes has a clear pattern in the way she fights. If she feels she can beat someone standing, she aggressively moves forward winging punches with maximum effort. Sometimes this doesn't result in a finish and she ends up gassing herself out. She's not a technical striker. She's more like Cyborg than she is Holly.
If she can't finish someone standing she desperately starts going for take downs. She did this against Germaine and she did this against Valentina. Taking Ronda down would be a huge mistake.
So let's recap.
The only way Nunes can beat Ronda is to duplicate what Holly did and transform herself into a counter puncher with precise timing or connect with a lucky punch. She can't bum rush Ronda or take her down and expect good results.
1. She certainly didn't "move straight ahead and throw bombs" against McMann, Bazler, and Tate. She gassed against Valentina she used up too much energy trying to finish her on the ground during the second; I concede that is a potential problem against Ronda.
2. Nunes broke Miesha in the standup, not Ronda. Nunes crippled Bazler with leg kicks. Nunes laid out Julia Budd faster and more convincingly than Ronda did Bethe. No way does Ronda hit harder than Nunes.
3. Nunes did a good job maintaining distance, counterpunching, and circling out against McMann and Tate. Unlike Ronda those two can shoot to better close the distance. Ronda has to strike her way into the clinch and eat punches doing so, which is a bad idea against Nunes.
4. I would agree if we're talking about the old Nunes, but the new Nunes wouldn't aggressively go for the kill in the standup unless she has clearly cracked her opponent, as shown against Tate and McMann.
I believe that Nunes can finish Ronda in the standup (the latter's no Germaine or Valentina) so I think it's improbable of her to go for panic takedowns. The fact that she's up against arguably the most feared grappler and submission fighter in her division would further dissuade such ideas.
I think Nunes is going to use the strategy she used against McMann and Tate, x100; maintain distance, pick her spots with jabs and leg kicks, counter with combos when Ronda comes close.