Don't be so hard on yourself. You said it your self; "she usually calls when she leaves and when she gets there". She didn't call this one time. I would think something happened too and would be freaking out. I probably would have called the police seeing if there were any accidents, I would have called the surrounding hospitals or started driving around looking for her myself. After my husbands accident I go nuts when I hear sirens when someone's not home. It's normal to worry. I don't think, she'll be letting her phone go dead anytime soon!

It sounds like you have a great kid on your hands.