It's not a matter of believing or not believing. To be honest, I have no idea who Calista's real enemy is, who doesn't know she's alive. I simply speculated on who could have done it, assuming we agree (?) with the statement that the original idea to plant the bomb on Kane (as a guarantee that Calista would keep her promises and not help him win the Gambit) belonged to Alexander.
So I don't know what to believe yet, but if Callista has no secret enemies, then we have to consider those we do have. And here, literally everything comes into play, from the potential psychological portrait of one sister or another to things like the fact that Jules hates Veronica, which means she's probably not too thrilled with Callista, whom V still idolizes.
So this whole situation with the bomb remote in Kane's body (if this "bomb" is indeed what we think it is) looks even more confusing than the “who is the 7th member of the Board and is it Astrid or not” question that we have already discussed a hundred times..As always, we have too little initial data.¯\_(ツ)_/¯