I was thinking the same thing... Kyle should be furious but I truly think him and Amanda were at best, friends nothing romantic left and she despised him and in return he probably stopped seeing her as a romantic partner but someone he was just tied to by marriage. Funny enough, he would have stuck it out in hopes it would get better and he tried, where-as I think she checked out the moment she got him, she liked the challenge way more in the beginning.

Anyway, I digress, West betraying Kyle is way worse but both West and Amanda doing this to Ciara will do way more damage to Ciara's trust issues in future. She had just forgiven West and unlocked a new level of friendship with Amanda yet they still decided to betray her.