So how was river and his family reaction to creek's betrayal?
Oof, it was not pretty. They're conjoined, so River was caught with Creek and taken to Bergen Town too. When Chef feeds Creek to King Gristle, she severs their hair from each other and leaves River in the cage with the others.
When they finally get to Creek, River is confused at first then horrified. Creek sees this and makes a comment along the lines of "I appreciate that this kind of thing is hard for you to understand, but you know that everything I've ever done has been what's best for you."
River swings hard into denial for the time they're in the cage, believing that Creek is stalling, and it's only until the rest of trolls are dumped into the pot that he is forced to accept that his brother betrayed them and turns gray with everyone else. Unlike everyone else though, she stays gray. (I haven't decided yet if he regains his colors. with everyone else and loses them again later or stays gray entirely)
Cybil stayed in Branch's bunker and was lured out with everyone else. She barely had time to process the betrayal before getting snatched up with the others. For a few long hours, she has a terrifying feeling that River is dead. Why else would she not have seen her with Creek? She is so relieved when she finds River in the pot, and she choses to bury her feelings about Creek's betrayal in favor of looking out for her youngest sibling.
I haven't decided yet if their mom is still alive at the time of the movie, but I can say that their mom was the type of woman with strong sense of responsibility to her community. She would also have chosen to bury her feelings about her son's betrayal in favor of supporting the village in the aftermath of being discovered and inadvertently neglect her other children's emotions.
Wind Breeze is.... a harder case. I haven't decided if she attends the party and stays in the bunker or remains in her home. And she has all those crystals showing her what goes on in the village, so she might've seen Creek betray them without actually getting caught. In any case, she's a very emotionally steady person and whatever turmoil she feels about Creek's betrayal, she choses to process in private.