Yawns equal sleepiness

Forty-five minutes after saying good night to Katelyn, she yelled for me to come to her room. It's not normal for her stay up that long so I checked on her and asked her if something was wrong. She told me she can't sleep, she's not tired. I asked 'why not?' She said, "I'm not tired b/c I don't have any yawns." I told her I'd rub her back to help her get tired and fall asleep. Five minutes later, out like a light:)