And there are ways to do wwehat Yvette attempted. But the way she did it only works if you haven’t fucked the person over once already, and all but guaranteed that they views you as the most evil individual to have ever existed.
Kane knows that the KG board was behind the assault on Seth and everything that resulted in Kane ending up in prison and at the Sadism Factory.
Olivia told Kane that the KG board most likely wanted him to punish the one responsible for what had taken place… which would be the KG board members. Yvette is a board member, who is now once more threatening Seth.
I can only assume that Yvette is either a double agent who’s trying to sabotage the rebellion while protecting her kids, or she’s so misinformed or out of the loop that she just doesn’t understand what she’s doing.
"The board" isn't a monolith. Even if they agree that Kane needed to be lured into the program we don't know if Yvette disagreed with the method, agreed, or just wanted it done and didn't care and just voted however Veronica did(this is implied to happen a lot). Alessandra was the one who was personally involved with the operation with Elena acting as the face to bring him in.
And even though the Karlsson Group has never been kind, the context of their nearly doomed world precluded that, from what was stated it only turned as vicious as we know it today after Alexander and Calista had their falling out and a now crazed Alexander raised the next generation of crazed leaders.
Yvette and Calista may very well have acted as a balance to the likes of Alexander and Elena in the old days.
This isn't to say she is kind, just not cruel. At least by the standards of that world. Her threatening Seth is just a plain stupid poorly thought out move on her part. Probably to illustrate that even the reformers are willing to play dirty, but still stupid since Kane is the wild card in all this and she has no idea if he can get to a position to retaliate against her or how else this can blow in her face. Too many unknowns with Kane to deliberately provoke him with his family. Especially a Dom Path one.
"Not understanding what she's doing" is the best description.
But nothing will happen. "Retaliation" isn't really the name of the game and Kane is most likely to over look that. Especially on a revolution path.
And like it was said, it's probably more bark than bite anyway. She's not Juliette after all.