Supposedly Soul Mates

Since the year 2300, a small silver pendant is given to every person on their sixteenth birthday. Legends say that the pendant becomes warmer when near a person's soul mate and colder when apart. Lindsey's mother has always told her that only two can fit together absolutely perfectly-if not, well, they aren't her soul mate no matter how much she may love that person. Typically, people go on a search to find that one other pendant that fits so perfectly with their own only days after they receive the necklace.
Even as she receives her necklace, Lindsey still is not entirely convinced that they work as perfectly as everyone says. It seems completely crazy, but as seemingly flawless couples surround her, it means the pendants work.... right?