Fun fact, since Yamao's introduction in chapter 883, as of chapter 1008 she has spent 20 chapters looking after Momo.
That's close to 80% of her entire existence as a character has been spent protecting, talking to and bonding with Momo, her future shogun.
And of course, what's especially significant about this relationship is that it's being newly developed. It isn't a Franky/Iceburg or Nami/Nojiko type of relationship. Old friends and family with a history together that straw hats leave behind to join the crew. This is a relationship that is only just beginning and is being developed for a specific purpose.
The type of development Jinbe and Luffy got together is the exact same nature as what Yamao and Momo are getting together, which comes as absolutely no surprise since Yamao's end is becoming Momo's guardian/retainer, not a straw hat.