She would protect him until she died. Having seen Trenzalore, she can pretty much promise him that. So if he wants to feel invincible, she will have no problems encouraging him. As long as the TimeLines remain properly intact.

"Not as much as I should like. Q is from an extradimensional plane. The Humans here belive him to be immortal, omniscient and omnipotent. Obviously, he possessed the ability to teleport himself and others. As well as the ability to time travel even across universes."