I don't think it's that simple. If Alexander's will meant nothing, then Veronica wouldn't need Callista (even setting aside the fact that she extols her as the only person who can understand her thoughts).
Do you think that opening that "final door" is nonsense and just a figure of speech? I dont think so. And if Veronica doesn't care too much about Gambit's rules, that doesn't mean she can refuse what Callista offers her in exchange for Kane and Seth being succeed. So I'm 100% sure that for all her independence, even V can't ignore Gambit completely and Callista knew where to push when she said that.
And now Callista and Veronica are in the same boat altogether, and I'm assuming they'll work as a unit and V will do whatever Callista asks.
P.S. And about the "bomb", we don't know yet how it works or who it is under remote control of. However, we do know (someone wrote about it here, referring to Yvette's dialogs) that if this enemy of Callista finds out she's alive, he can kill Kane immediately.
I have no doubt that V will pull it off, but so far we have no idea what it is or how to retrieve it. Maybe it's some kind of nano-bot hanging from a key artery leading to the brain, which on remote command could be immediately clogged or severed and "hello, Valhalla". So I wouldn't oversimplify things here either.