My 9 year old daughter has mild fever 100.3 and a toothache back tooth?

See DDS: These may be disconnected symptoms, but...If they are connected, this can be important. Toothache may reflect a dental abscess which, if it extends into the depths of the head/neck, can be fatal. Toothaches do not get better by themselves. Take your daughter to the dentist.

Fairly common: For child's temp to elevate during teething, but keep monitoring.

Seek Advice: The fever may or not be related to the toothache. I would consult a dentist if she is having severe tooth pain. If not, i woould consult your physician if the fever continues.