There was so much confidence when she called him but now she had some self-doubt. Why did she call? She found it easier initially but with the timing being wrong, it was a quick retreat.
Ignoring his question she just said, "If you're sleeping, I'll hang up." It wasn't that she wanted to keep him or make him chose between sleep or her. She truly felt that it was only right she hung up and completed the call either. To add, there wasn't anything important to discuss, meaningless chatter aside.
