If you guys are going Social then go Adorjan or if necessary Malfeas.
Why? It's fine to like those charms better and that's definitely a valid character generation approach (though for personal opinion I definitely love Kimbery more than either of those.)
But in terms of actual character advantage neither plays well to Nami's social strengths. Malfeas in particular synergizes poorly with Nami's fiend ED set in general. If you're not trying to add the complication of a hilariously inappropriate Malfeas charmset that should be the single easiest choice on the list to discard.
ED has much of the strongest social offense in the game. Malfeas and Adorjan both tend more toward charisma in charm requirements, and Malfeas in particular is almost hilariously awful for Nami's personality and preferred strategies. (It could be fun if we want to really push her far away, but it's hilariously suboptimal if that's why you're suggesting it.)
I mean, she's very much the emotionally manipulative trickster who lies to everyone and messes with your perceptions. She's not at all a "Go around ordering everyone to obey with pure force of personality." Look at her actions on the weather island for Nami being socially manipulative, or every crew she joined and tricked while working with Arlong.
As for Adorjan social, Theft as Release is pretty much all we'd really get out of that that we could use well. Maybe Tragic Love Amusement stuff or Dissonant Lies Made True, but most of those are explicitly tied to charisma.
Personal opinion is personal opinion, and it's perfectly wonderful to use it as a deciding factor. But it's also pretty individualistic. However, in terms of actual pragmatic arguments Kimbery seems to come out hugely on top when you consider that we already have a social strategy via ED.
Kimbery has crazy synergy with the setting (ocean is everywhere powerful sea monsters exist.) Kimbery also has some great social defense though it does get boarded behind Intolerable Burning Truths which would make Nami a little.... interesting maybe if we really go that route. (Not that ED isn't sufficient for becoming a social monster.)
But, let's look at Kimbery charms and see the best/most awful options for the One Piece world. None of this considers Kimbery's general awesome social defense suit, passive UMI abilities on par with Malfeas, interesting poison powers, etc.
Mother Sea Mastery: Super speed underwater, Swim 2-5 times faster than normal, no fatigue for swimming once she gets a bit of power (IE: She could swim around the world without stopping. Combine with a small Adorjan dip for super speed and she'd have every reason to say "Fuck the boat" and just dog-paddle the grandline. Basically gives her the full merman underwater package. Even if we don't favor Kimbery the benefits here justify the one charm dip.
Ichor Flux Tendrils: Or "Lulz devil fruits." because the ability to telekinetically attack people with the ocean pretty much shuts down a devil fruit powers or at least really gives us a huge leg up on a ton of them. Moreover it's a weapon that doesn't key off Nami's tertiary physical stats or low combat abilities. Meaning even if we dump fighty stuff we can still contribute importantly to battles. Might not always be available, but whenever we're near a boat or the ocean we'll have combat power getting near a logia user. (It keys off force of will+essence, both of which everyone should want to max anyway)
Fathomless Poison Haven: Oh look we can grant people immunity to harm from any liquids including poison. Not sure how it'll work with devil fruits, but potentially a setting breaking power by itself (And making people drown/pressure-proof is pretty nifty on a boat even if it can't cure that flaw.) (Also hah Impel Down arc if we get that far.)
Acid Slipstream Assist: Nami's the ship's navigator. This lets her move a beloved boat (like the Going Merry will become if we stick anywhere near canon) twice as fast as she can swim. Best Infernal charm to make a ship go where you want. Given that she'll be able to swim super fast, this gets pretty crazy.
Kimberry's Flaw of Invulnerability: We get PD as long as we're near the sea. IE: Almost always.
What Lurks Beneath: Summon sea monster. Look at some of the stuff that lives in the One Piece Ocean. Tell me you wouldn't want to be able to play with those things? This lets Nami call them at will from anywhere and have them appear in a few minutes.
+A lot of other stuff that's useful in general and not just because of One Piece's setting.
The way I imagine it, Nami's fiend caste ED charms will give us social offense, disguise and infiltration powers that hit Nami's core specialties as a thief. Kimbery matches her navigator character traits power, and gives us the power to be more than relevant in combat situations despite poor physical stats while also adding a ton of utility around the water and shoring up our defenses both socially and physically.*
Aside from that we'll want maybe 1-2 Cecelyne charms, a few SWLIHN bits like factual determination and some Adorjan, all of which could be done at chargen or spread out later.
*(Granted going full on Golden Years+Intolerable Burning Truths makes it
fun to try to play a nice character, but Adorjan and Malfeas aren't much better in their social options there.)