The 36-year-old TV personality and daughter of David Foster got engaged to her boyfriend, Simon Tikhman, while in Napa Valley, California. Erin shared the exciting news on her Instagram on Tuesday, alongside a photo of herself in a blue-and-white floral dress and her hand on her face looking shocked.
"How on earth did I pull this off ?," the newly engaged Erin captioned her post, which quickly got filled with congratulatory messages from her friends, family and fans.
Kim Kardashian West commented on the post, writing, "OMG CONGRATS!!!!!" while Sara and Erin's stepmom, Katharine McPhee, put three faces with hearts emojis, and Gwyneth Paltrow wrote, "Awwwwww."
A source told ET of the engagement, "Erin was completely caught off guard with the surprise proposal over the weekend in Napa after Simon had been working on it for weeks. The two are head over heels in love with each other and over the moon to celebrate this moment with their loved ones."
In addition to her Instagram post, Erin took to her Story to share just how her guy pulled off the epic proposal. "A month or so ago, Simon told me his friend was doing a wedding renewal," she shared before posting the fake invite that Simon made.
He then pleaded that they get a couples manicure before the big event, but his finger got infected from the pampering. From there, the two flew to wine country and got instructions about the event at their hotel. Little did Erin know but her sister, Sara, stepmom, Katharine McPhee, and father, David, were hiding while she and her soon-to-be fiance toured Napa Valley Reserve.
"When we got there, there were balloons and signs for this fake a** wedding," she recalled. '"We walked in to the most beautiful place I've ever seen."
"Nothing has remotely dawned on me at this point. I'm definitely not as bright as I thought," she quipped.
Erin was in complete shock when Simon got down on one knee to propose with a Martin Katz ring. That's when all the family members revealed themselves and Erin continued to be in a state of surprise. Erin said this was the first time "our families have ever been together," and they all enjoyed a dinner before Katharine and David performed.
As for Simon's finger, Erin concluded her posts, "The moral to this whole story is really to be careful where you get manicures. Our post engagement was spent in a doctor office getting Simon's finger drained and now he's on antibiotics."
In July, Erin posted a black-and-white photo of her and her beau, jokingly writing about not getting engaged during their vacation.
"This man took me to Italy for two weeks and didn’t propose," she captioned the pic.