So see for Nami she had exactly 2 people who were her closest everything. Her only living family (MC) and her best friend (Summer).
When people go through pain and sorrow what they need is their support system to help them through the troubles. But for Nami her 2 people were the ones causing her sorrow and pain. No way a young lady that age goes to her Mom and also Nami would be even more reluctant if she has romantic feelings causing her pain and she knows that is Taboo and not accepted.
Bella has friends (Ayua at a minimum) and a supportive (NOT DEAD) Mother. Plus having money means she doesn't worry about many things other young women might (Salon stylist hair, fashionable clothes, transportation that also looks cool) so she is about as light on hard knocks as you can get other than her losing her sister. (Another one who may not be dead??)
So in spite of this Nami has been the rock for the MC while he goes through this (overblown IMO) trauma. (Unless she died in front of him, then I might allow this level of moping). Nami did this with her own loss of Summer (her BF remember). Nami is simply an exceptional, empathetic human being. When we see her at the gym we see how she is this wonderful person to many people not only the MC, like her selfish love for him doesn't makes her nice, she just is nice.
I know there is a whole trope for the Tsundere but Bella is a rude ass bitch way beyond any need and I do not get how that turns people on. I do not mind helping Bella be a better person. Why? Because that's what Nami would do and she is a great person to emulate, BEST girl in fact.
But long term I want Queen Nami to get the best of my love!