I really can't see the logic behind the fact her protection gain isn't stopped by healing immunity like ALL THE OTHER PROTECTION REGEN in the game, such as the different leader (zeta) ability or character like Boba. It's not even a "protection up" buff that can be prevented or dispelled, it's just, for all intent and purpose, virtually identical to protection regen except the regained protection is purple and reset under certain condition. I don't see why it shoudn't be prevented by healing immunity for consistency.
It's not like it would cripple her: Character with healing immunity are not exactly by the hundreds, let alone the vast majority of them aren't even close to be meta.