Yamato: let’s ask Luffy and the others for help!! They won’t lose to a guy like this!!
Momo: that’s not helpful! I won’t need your help either! Don’t offer it!!
Momo: pant pant
You’ve been locked up on Onigashima almost you entire life!! But now you’re free!!
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Momo: and that’s why!! I want to send you off!!
Luffy, Zoro and the others…I can’t always count on them for help!!
We have to be able to fend off all enemies on our own!!!
Momo: if we rely on those about to leave!! How can we protect our country in the future
This confirms or at least strongly implies two things (which were almost obvious, anyway):
1) Zoro is stronger than Yamato
Yamato can't do much against Green Bull but believes that Luffy and the others would be able to; Momonosuke say they can't ask Luffy, Zoro and the others, implying that at least Luffy and Zoro would be able to fight Green Bull)
2) Yamato will join the Strawhats and set sail
Momonosuke wants to send her off together with the Strawhats and seems to imply that she will leave Wano, so because of this he needs to be able to take care of things