Lauren Sanchez Wears New 'Mrs. B' Bling at Dinner with Fiancé Jeff Bezos

Make way for Mrs. B! Lauren Sanchez was out for dinner at Nobu in Malibu with her billionaire fiancé Jeff Bezos and pals Wednesday ... rocking a jaw-dropping new piece of bling.

The former TV anchor's 20-karat engagement ring -- reportedly worth $2.5M -- clearly isn't enough to cement their pending union ... as she took a subtle "Mrs. B" gold necklace out for a spin.

Whether the "B" symbolizes "Bezos" or "billionaire" remains a mystery ... but one thing's for sure, the chain was putting all focus on her decolletage ... complementing her plunging all-black look and pink-lined coat.

Lauren is clearly loving every moment of their engagement ... earlier this month she posed for a western-themed spread with Jeff, and told the fashion bible they haven't made any headway with wedding planning yet.

While we can only assume they'll hire a team of wedding planners to diligently orchestrate their A-list nuptials ... the duo is currently engrossed in planning a cross-country move.

Jeff recently announced their plans to relocate to Indian Creek Island in Miami Beach ... closing the chapter on Seattle, where the businessman founded his iconic tech company.