This is really happening! Hailey Baldwin has started her wedding planning with her mom and with an event coordinator and we spotted her out at Revelry Event Rentals in Downtown LA Thursday starting the work!

As we all know, Justin and Hailey are already married -- just look at that ROCK on her finger! But they're organizing a ceremony for friends and family in the spring since their previous nuptials involved a quick visit to a New York courthouse to get their marriage license with no one but the two of them in attendance!

This event rental company is the same one Kris Jenner used to put on the family's insane annual Christmas party a month ago -- an all-white, fuzzy, Whoville-themed event. No doubt Hailey's likely enlisted the help of party-planner to the stars Mindy Weiss to oversee all the details. Despite reports the ceremony will be small and intimate, we have a feeling it's STILL be over-the-top!