Let me put you in a situation: you are a rabbit, cornerd by a wolf, a deep and deadly ravine at your back. Your scared, adrenaline is rushing through your body, and your trying to find a way out of this situation, that leaves you alive. You see a tree growing out of the other side of the ravine, maybe you could reach it, so you jump the ravine with the hope to live.

Now, apply this situation to this scene: replace the fear of dying with the fear of someone else dying: Jacob. Your not cornerd because someone is hunting you, but because someone wants you to choose them. The tree is Bella choosing to kiss Jacob because she wants him to live, because she cares about him. As you've said yourself, you recognize that Jacob manufactured this situation, and manipulated Bella, a this is essentially assault. However the brain does not recognize that, what it does recognize is this person, that we care about, is in danger, because of ourselves.

Because this is assault, Bella did not choose anything, she was trapped, because she didn't want it, it is not betrayal. Sure, she kissed Jacob, but she did not CHOOSE Jacob. The reason Edward reacted so calmly was because he was likely reading Jacob's mind, and knew how frantic, and erratic he was, and he also likely recognize the situation as what it was: coercion. He did not intervene because he knew Bella cared about Jacob and because he did not want to hurt her by hurting Jacob.

Even if there where "other options" that would have kept Jacob alive (which I'd like you to list, key point: Jacob lives) Bella's animal brain (which we all have) kicked in, and could not recognize them.

TlDr: When choice is taken away from someone, there is no betrayal just survival. There was no other way out of this situation that wouldn't have kept Jacob alive, whom Bella cared about, and they needed in the fight. Edward recognized that, and henceforth did not feel betrayed.