So her advice for Kate Middleton on her big day is simple.
"It's an incredibly difficult role that she is going to be taking on," Hicks tells PEOPLE. "What will be particularly difficult is finding the balance. The world will be sharing that day with her, yet she must bear in mind that it is her wedding day. Kate must enjoy it intimately with her family and with the man she loves and will spend the rest of her life with."
Hicks, a fine jewelry designer and creative partner with Crabtree & Evelyn, will host the TV special Untold Stories of a Royal Bridesmaid on TLC, airing Sunday at 9 p.m. ET/PT. She also offers a recommendation for both Kate and Prince William for post-wedded bliss: Work as a team.
The royal couple must "remain extremely close and bonded," says Hicks. "Marriage is incredibly difficult as it is, without the world watching. So one can only hope that they remain a very, very bonded team and find the strength to go through it together."