When did my daughter become me as the mother?

Role reversal is happening.
Yesterday Helen and i were crossing our very busy road and i said "i can't see the cars coming!" because a 4 wheel drive was blocking my view.
Helen said, "don't worry." I can see," she says grabbing my sleeve. "when i say go, we go!".
Half way across I'm thinking oh my God, i just put all my trust into her hands and hoped that we would get across in time.
When did she grow up? It has happened in a blink of the eye.