I think you’re overreacting.
Chill.
If you haven’t heard from her in a week, then you may have a problem, but if it’s only 16 hours since you saw her, and you’re freaking out because she hasn’t responded, I think you need to get busy with homework, a job, a sport, a hobby, family, pets and friends. This is more about your anxiety then it is about her behavior (which right now, is normal). 😉