'Southern Charm' Alum Olivia Flowers Is Engaged to Alex Williams! All the Details from the NYC Proposal tram

Olivia Flowers is engaged!

The Southern Charm alum's now fiancé Alex Williams, 34, popped the question on September 25 in a New York City proposal that involved Flowers' parents — and weeks of planning.

Speaking exclusively with PEOPLE about the proposal, Williams reveals that Flowers' parents and many of her close friends were present when he asked her to marry him in the Meadow Terrace Suite at JW Marriott Essex House. According to the couple, Williams got down on one knee with a custom 4-carat diamond ring from Nicole Rose Jewelry which featured an 18k yellow gold band and a "classic, simple and elegant" style.

Williams began planning the proposal earlier this month when Flowers left their home in Dallas to attend New York Fashion Week. As soon as she took off for Manhattan, Williams secretly departed for Charleston, South Carolina, where he asked Flowers' parents, Garry and Robin, for permission to marry their daughter.

"Olivia has such an incredible group of friends, from elementary school through to college, and she's very close with her parents, so I knew involving them somehow would mean a lot to her. I wanted her to feel all the love and the excitement in the world from the surprise of her loved ones," Williams says. "Her mom Robin had the idea to propose while the four of us would be in New York together, for the Project Lyme Gala Olivia was speaking at."

According to Williams, the planning process wasn't without its challenges as his itinerary changed last minute due to a United Nations meeting in New York City the weekend of the proposal.

"The JW Marriott Essex House staff and our friends and family were so accommodating and moved well as the plan evolved," he adds. "I told her we had a work event to go to at one point and then I changed this to a luncheon, then I got her brand manager involved and made her thing it was a photoshoot for the hotel."

"It got a little hectic, but luckily Olivia was incredibly busy with her Project Lyme speech, so she didn't catch on to anything at all," he teased.

By the afternoon of the 25th, Williams had secured all of his plans, and at 3 p.m. that day, he and Flowers made their way to their recently-upgraded room at the Marriott, where a photographer was waiting for them to grab some social media content.

"He is my biggest hype man when it comes to helping me with content so this didn't seem weird to me, just like a sweet gesture.... he actually got my social media manager involved so I thought this was a brand deal, so I was in work mode," she joked, adding that she immediately took out her phone and began working out the best angles for photos in the room.

"Next thing I know, Alex is getting grabbing a box out of his sports coat and dropping a knee... then I drop my phone," she joked. "Alex said, 'Olivia Barbara Ellen Flowers. You're the girl of my dreams. Became the love of my life. And I’d like to ask will you marry me?'"

Flowers jokes that she can't believe how unaware she was throughout the entire process.

"Looking back now it's concerning just how many things I didn't pick up on, but it made for a good surprise. Or several surprises, I should say," she adds.

Shortly after, Flowers' parents and nine of her friends came "piling" into the room.

"I could see it on Olivia's face after the proposal that she was so excited to call her people and share the news, so arranging to have them be there and surprise her was so much fun," Williams says.

"We opened bottles of champagne and Olivia's favorite wine and celebrated with everyone on the terrace. We later went to Olivia’s favorite Italian restaurant in NYC, which is also where Alex's brother and wife surprised them, Trattoria Dell’Arte."

The surprises didn't end there, either — Olivia thought that after the night of fun ended, her parents would head back home to Charleston and she and Williams would go to Dallas. But when the newly-engaged couple arrived in Dallas, they went straight to another restaurant (the Nelson, located inside the Ritz Hotel in Las Colinas) to continue the celebrations — and both Flowers' and Williams' parents were waiting there for them.

The pair, who met at a wedding last year, spoke about how meaningful Dallas is to them as a couple — especially because they may have even crossed paths there growing up as teens.

"Dallas has always been a happy place to my family and I, my brother and I lived our high school years here and have very close friends here so to have a celebration there with our people colliding was so incredible," Flowers recalls. "Our families were both members of the Four Seasons Country Club."

"It's so wild to think Alex and I were in the same places growing up but never crossed paths!"