Possibly. Probably even.
They do have the ability to turn her unique off for a specific event or TB battle or whatever. The problem here is that immunity to TM manipulation is the level 1 version of her unique. If the unique is unlocked at all, then the whole squad is immune to TM reduction. But if the unique is locked for the battle, then none of her allies get the bonus protection & courage effects.
That's a pretty huge loss to a Padmé squad, and it's hard to imagine them giving that up.
So while it's technically possible to turn that ability off and make this feat possible to accomplish, it's more likely that -- assuming your info is correct -- the Challenge is bugged.