Are there neuron mediated reactions faster than reflexes?
A reflex as fast as the blink in a neural circuit:

I would consider suppression of outer hair cells in the cochlea to be a reflex; the faster component of this reflex is about the same as the blink reflex, around 100 ms. The hair cells themselves aren't considered neurons, but the pathway that suppresses their motility certainly is.

A much much faster non-neuronal "reflex":

That said, the outer hair cells themselves also dance along quite fast in response to sensory input, even faster than the typical hearing range for humans, faster than 20kHz! In some ways, this is a reflex because you are taking sensory (specifically, auditory) information and turning it into a motor response, but all the "action" is taking place within one cell, and it isn't a neuron.

A more classical reflex that is substantially faster than 100 ms

Reflexes in the periphery can be much faster than 100 ms. The myotatic reflex, or stretch reflex, can be as fast as 30 ms in the knee - this is the reflex that is tested when a physician smacks you on the knee with a hammer (used as a test of spinal and peripheral nerve function, not as a punishment). It's likely there are other stretch reflexes that are faster just because distances to the spinal cord are shorter, but these might be more difficult to test (in this paper they report latencies as fast as 20 ms).

Eyeblink reflexes can also be faster than 100 ms!

For example, see this paper: strong auditory stimuli evoked blinks within about 20ms!

tl;dr: I'd check your source that 100 ms is the fastest reflex! I stuck with mostly human examples here (some of the hair cell work is in other mammals), but you will find even faster reflexes if you look at smaller organisms, such as insects.