I know she said that, but I think you're taking her words too literally. Yes, Aura doesn't work until it's unlocked, but I don't believe it has to be consciously activated to protect you. For example, Jaune's Aura healed the cut on his face all by itself, without his direction. I suspect that Aura can protect a person on its own, at least partially. For a more solid defense, conscious activation is required. That's my theory, anyway.