Reinhardt, 29, married Sean Brown at The Resort at Pelican Hill in Newport Coast, California, on Saturday, revealing the happy news with several stunning wedding photos.
"Last night was the most magical, incredible, most emotional night of my life!!!" she captioned an Instagram of herself kissing Brown on Sunday. "I became Mrs. Casey Beau Brown and I get to spend the rest of my life with the most amazing man who ever walked this earth. I'm so happy, so in love, and so overwhelmed with emotion just thinking about how beautiful the rest of our lives are going to be together. You are my angel on earth @seanmbrown1 and I'm the luckiest girl in the world to be your wife!!!"
The bride looked like a princess in a lace ball gown and flower crown adorned with a veil. The lavish reception featured fireworks and a performance by Sara Bareilles.
Brown popped the question in August, proposing with an enormous, pear-shaped diamond.
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Reinhardt, who owns bakeries called Casey's Cupcakes, appeared on MTV's hit reality show during season 2 and the spinoff The Hills for a eight episodes while Lauren Conrad dated her brother, baseball player Doug Reinhardt.