Well, diagnosis negative is the accurate title, but bonus points to anyone who can identify the source.
Anyway, pediatrician suggested cough suppressant, since the cough is mostly horrific at night. If it's still bad, bring her in Monday.
Clinic turned out to be a breeze. But the strep test was negative, lungs are clear, so just (just!) a cold. Warm liquids, rest (ha), cough drops.