Almost too Close

Welcome to our world. The world where you're born with a necklace. A necklace that leads you to your true love.
But there's a catch.
Fail to find your perfect other half before you're 20 leads to death for the both of you.
It shouldn't be hard to find them... should it? It gets warmer when you're closer, and glows when you find them.
Our names are Violet and Ashelley Houston, and this is our story.
Take our word for it, it's a lot harder than it looks.