Newly confident, Mary says yes. Notice that she does so in absolute freedom. No one coerces her. And she was free to say no. Mary also makes her decision without appealing to a man. She doesn’t ask Joseph for permission. Nor does she tell the angel that she must consult with her father.
Overall, being spiritual and being religious are both part of being in relationship with God. Neither can be fully realized without the other. Religion without spirituality can become a dry list of dogmatic statements divorced from the life of the spirit. This is what Jesus warned against.