You just know that every single Quiet Council meeting ends with Mystique turning to Xavier and saying "That's nice. Now when are you bringing back Destiny?" with increasing acidic stares and tone. She probably already has napalm bombs or something all over Krakoa in case they try to screw her on this.
If she found out that Betsy is helping and working for/with the guy responsible for the giant monster invasion in the first place, her attitude might change. And I don't know how much of the going ons of the otherworld the British government is privy too.