Oda seems to be doing something interesting between Nami & Big Mom.
Theres been this underlying question between them that seems to be asking: “who is superior?”
Like back on whole cake Nami asks the homies “whos more terrifying me or big mom?” And they immediately choose her.
Nami forces Zeus to choose between her and big mom during whole cake and he chooses her out of fear.
Then on Wano Nami forces Zues to choose again, tells him he has a choice to make “me or Big Mom?” and Zeus is eventually swayed back to Big Mom’s side but the ultimate point I’m making here is that theres a back and forth going on here. A tug of War. A battles of wills taking place between Nami & Big Mom.
Then here in this chapter Oda has Nami defend Tama before the World's Biggest Mom is able to do so. Almost as if he's making Nami out to be the better mother figure and the true defender and protector of Children. Because while Big Mom is angry that someone who fed her was harmed Nami is angry specifically because Tama is a child not just her friend or someone who did her a favor. Nami views all children as precious and worth protecting while Big Mom only cares if they've been useful to her. The scene hits even harder when you consider that Nami is significantly weaker than Big Mom yet despite that she’s willing to face a far more powerful foe for the sake of Tama yet Big Mom the more powerful “Mom” barely moves when Tama is hit. Nami was exuding REAL Mommy energy here and her Motherly Nature surpassed Big Mom’s in this instance. Ironically making her a Bigger Mom than Big Mom.
But this scene also serves to further highlight the flaws of Big Mom as a Mother. Big Mom only cares about a child if they were useful to her. This also explains why she didn't help or care about Momonosuke when he was about to be executed. Momo was never useful to Big Mom. Thus Big Mom never spared him a thought. Whereas Nami views all children worth protecting. This is actual motherly behavior. Something Big Mom lacks. This scene also shows Big Mom's callous neglect of Tama's feelings. She cares about Tama only because she was useful but is also willing to murder Tama’s friends just because she doesn't like them. Showing a complete disregard for how Tama feels as a person. This is again, another flaw in the mothering of Big Mom.
So in addition to all the tug of war between them and Zeus, Oda seems to be deliberately showing us Big Mom’s flaws while holding Nami up as superior.
So yeah, I think Oda is setting something up for Nami. Something that forces her to surpass the will of Big Mom. He’s making her compete with the most fearsome woman in the world and I can’t help but think Nami is meant to take that title from Big Mom. Maybe even giving Nami a reputation that exceeds the most powerful Woman in the world.
TL;DR: Put Respect on Queen Nami.