Mystique is a pro-mutant terrorist! She will resort to any means to take out groups that threaten mutants, poison gas, bombs, nothing is off the table for her! She will threaten their families and their children and follow through if they don't do what she asks! I can't see her working with Orchis, I see her assassinating members of Orchis regardless of Krakoan no-kill laws!
Didn't Mystique throw her own mutant baby off a waterfall?
You never know what she'd do.
Let the flames destroy all but that which is pure and true!