Thought: maybe your friend was folowing a cycling tradition and had decided you should be her domestique?

Just kidding. Seriously it was unwise at best of her to ride without something so essential to her health. She's lucky she did not need it, because if she did even if you were right beside her it would not be fast enough. I've learned one rarely makes friends by pointing out to them that you are right. Hopefully she will come back around 8-)