About Amber: Bella thinks of Amber as someone special, which is why Nika says:
d "Ohhh, now I get it... Your mother is holy."
So Bella could just be thinking that Ceril would love the prestige of charging Amber's daughter. BUt when we find out from Mila how Bella was bullied by Melanie Ceril:
mi "And Melanie picked on Bella because Amber complained about Melanie at the school."
It could just as easily be a petty grudge, the older sister, the whole family having a grudge against the Von Halen's. Or not, it could be something we don't know yet. There's not enough explanation, and Bella's not reliable as a character witness
About Nami, she gets upset because Nika opens up to her, then starts playing the field. If there's no change of perception, the scenes are different from memory. It's natural that the very same day Nika says he's noticed her in a different way, Nika might go with Bella, Nika might kiss Mila, and Zara is affectionate to him when the day before she wanted to kill him. Nami's emotions will have been on an absolute rollercoaster in that situation - the night before she was pretending she was normal, but almost started kissing Nika in a fourway pash, the next day Nika confesses feelings, then he kisses other girls in front of her in less than 12 hours. She's GOT to doubt his sincerity. ON the other hand, she will be Nika's wingman and joke if there's no change of perception. She's completely able to be part of things by the way she accepts Vic and Nia. Much the same as Mila or Kate acting different if Nika's kissed Bella or not. I think the rumours will play a significant part in changing the perception of relationships.