This concept of "the word" refers to the most basic, most simple, and most fundamental forces of creation. The smallest original vibrations, which are used to create all of the more complex forms of everything that exists. As all forces, all physical things, and everything that exists are really just a collection of vibrating energies.
Before "the word" of physical creation, there was only the "silence" of the Aether. But the Aether is not nothing, it is the infinite and endless source of potential energy which has the possibility of becoming anything, and all things. As all things, before they existed they first appeared as a ripple in the field of the Aether, and this ripple grew to a larger vibration and an increasing strength until it eventually became what it is now.
Lilith is the Goddess most closely related and connected with the Aether. She is the closest to the endless infinite waters of the Aether, and the surface of this field which all creation emerges from. This is what Lilith is the symbol of, and what she is in charge of. In this way, Lilith is in charge of "the word" of creation which emerges from the original silence.