Four hundred and ninety-six days until Kristin Cavallari's debut book Balancing on Heels drops, and today she points us to a mystery. Might she explain this mystery in her book? Hard to say, but here it is: If Kristin had to pick one person as her best friend, who would she pick?

Kristin presented this mystery to us by Instagramming a photo of "BEST BITCHES" necklaces today, urging us to go to EmeraldDuv.com and purchase them as a set for $55.

Emerald Duv is Kristin's jewelry line. She likely designed, or at least picked from a set of designs, this "BEST BITCHES" necklace set. She also probably got one for free. So who got the ST CHES part of Kristin's set?

Who is Kristin's Best Bitch?

In 2004, Kristin's Best Bitch was fellow Laguna Beach castmate Alex H., if you asked Alex H.

In 2010, Kristin's Best Bitch might have been her castmate on The Hills, Stacie the bartender.

But Kristin's 2015 Best Bitch remains unknown. Maybe it is her jewelry design partner? Or her toy Yorkie named Bardot?

Or maybe it is Millionaire Matchmaker Patti Stanger?

I guess we might find out someday.

This has been 500 Days of Kristin.

[Photos via Getty, Laguna Beach]