Absolutely agree. There are two sides of Nami that cast a slight shadow on the shining image of the ideal girlfriend for the MC that we see at the beginning of the game.
The first thing was summed up perfectly by
John972, Nami had clearly done something in the past that hit the MC hard. It is also clear that she has changed, but the fear that she will return to her old self is bugging the MC.
But what exactly she did is unclear, and we can only speculate. She may have been trying to break up MC and Summer, and since they were friends, she dragged her on dates with other guys, trying to set her up with some jerk and hence the MC's constant fighting at school. Or maybe she was so desperate that she played the "I love you and I'll kill myself if you reject me" card. But when he returned her feelings, she chickened out and started gathering assholes around her to stop the MC from trying to go further in their relationship. Typical teenage drama queen behavior.
Damn, I both love and hate it when Ocean plays "Lost", making up mysteries and herding the red herrings. But there is a high risk that in the end the answers will turn out to be as retarded as in the “Lost” finale.
The second thing is, as you correctly pointed out, Nami seems to be very jealous type, even more than Bella. Moreover, it seems to me that she will absolutely calmly accept the physical intimacy of the MC with other girls, she may even encourage him to have a threesome, but she is very jealous of any emotional connection with anyone other than her.
As you follow Nami's path, she constantly keeps an eye on Zara in chapter 5. When Zara sits on MC's neck, Nami immediately asks with displeasure what she is doing? Later, at Nick's house, when Zara is left alone with the MC for a while, Nami again displeasedly asks her if she is going to help unpack their things to take her away from the MC. All this doesn't happen if MC is cold to Nami and not on her path.
Another funny moment. Whenever I play Bella's route, when Nami asks how serious the MC is about Bella, I always answer, "I'm starting to fall for her." This obviously hurts Nami, but she quickly regains her composure and diverts attention by cracking a joke about "romance and
fisting". And she says she will help the MC and
Bella is in for a treat. But suddenly I tried another answer “Just the right amount, duh.” and Nami didn’t seem hurt much, she sincerely said that she would help the MC with romance and
petting, and
the girls are in for a treat.