Although it was clear Castiel wanted desperately to attack Morningstar, God knew he wouldn't without her express permission. Just as she knew Morningstar wouldn't dare turn against her right here and now, and try to sway some of the lost souls currently gathered to her side. No, God knew they would behave - as much as an angel as young as Castiel and one who had fallen so far as Morningstar could at least - and therefore she felt quite comfortable with turning her attention away from them after a while to one person in particular.
Nathan Petrelli. A man who had spent the bulk of his life living up to expectations laid out by his father and whose ideas, while certainly not ones that God balked had, had landed him in quite a bit of trouble and caused no small amount of pain to others in his life over the years. He was one of the current lost souls assembled. A man who, while undoubtedly certain of her existence, had still managed to lose his way in a world that had spiraled out of control around him.
Rising, God moved past Morningstar - with a warning look to both her and Castiel that all but screamed 'both of you behave' - and slid into the empty space beside Nathan. He was still struggling, even know in this place of worship. She could sense it coming off of him in veritable waves and made a decision as she gazed upon him to do something she rarely did with most humans.
She intended to make her presence known. Once she'd done so, she knew it was quite likely she would have his full attention. Until she did so, she knew he would pay her very little mind. And in order to help him, she needed him to know who she was and that she was truly there.
It wouldn't take much. Her Will alone could, of course, make him realize it. As could a great many other things she could do to draw his eyes upon her. However, she wasn't about to strip his own free will from him nor did she wish to make a scene and cause the others assembled to glance their way. So instead of anything flashy or impressive, as many likely believed she would do should she truly walk amongst them, God did something rather simplistic.
Reaching out, she placed her hand upon his shoulder and allowed her simple presence to be felt clear to the depths of his soul.