You were born blind. You had never seen any color or anyone you knew. This didn't make you weaker however, as you had the power to be able to sense vibrations in the ground and hear exceptionally well to be able to get around (Think of it like Toph from The Last Avatar, except you can't earth bend since that's not a think in Steven Universe, you're kinda like a spider if that's a way to explain.) When you meet Spinel she realizes you're a lot more sensitive and depressed then she initially thought. And so decides to go through with what she wanted all along, and become your best friend...your eyes...and....maybe more.