None of you see to be considering what part her wolf played in her feelings for Declan. I got the impression it was her wolf who claimed Declan first and it took Stacia awhile to get with the program and look at Declan in a new light. I mean, in Rogues, she is clearly conflicted and doesn’t come to her senses, so to speak, until several of the men staying at the hunting camp point things out to her. But again, the wolf knows.
As for Tanya’s behavior – people and perspectives change. In the beginning, when Stacia was trying to take Chris away from her, Tanya was insecure and jealous. Then, after Trent died, she had a huge revelation and it changed a lot of things for her. So, Stacia is no longer a threat. Tanya knows she’s been with Chris basically since the beginning of time and no one is going to change that.