The word you are thinking of is vitreous.
What? You say you don’t even know that word? Don’t lie to me. It is the perfect word, the word you think of when you search desperately for a word to describe this relationship you are so inexplicably clinging to. (You used to trot out fissile for this same purpose, but it just sounded so awkward when you said it out loud, and most people didn’t even know it was a word, let alone what it meant.)
It seems no coincidence that it also perfectly describes the look in your eyes whenever she walks into the room.