If this is helpful:
Any illness that causes a fever (high temperature) can cause a febrile seizure. Most occur with common illnesses such as ear infections, coughs, colds, flu, and other virus infections. Serious infections such as pneumonia, kidney infections, meningitis, etc, are less common causes.
About 3 in 100 children have a febrile seizure sometime before their 6th birthday. They most commonly occur between the ages of 18 months and three years. They are rare in children under six months and over the age of six years.
So, I'm wondering if your DD may have had some low level infection of the ear, or just a cold which, because of her genetic dispostion, led to the convulsion.
If your DD had many, and is therefore particularly disposed, it could follow that a lower level infection might more easily trigger a seizure in her (as opposed to someone like my DD, that got her first when dealing with quite a severe infection and a very spiked temp).
The research shows that a body temp of 39 degrees is usually the point at which a seizure is triggered, although the threshold is genetically determined - so VS, it is POSSIBLE that your DD has a lower threshold than the norm. Which would account for no obvious presenting symptoms when she was examined.
The other thing worth noting is that it is generally considered to be the RAPID ASCENT of the the temperature that causes the seizure, not the actual temperature itself. So it's not suprising that a child goes from nothing, to seizure. The seizure is usually the first sign of the infection.