The singer and TV personality, 58, plans to marry her longtime business partner Jeffré Phillips, who popped the question while the pair vacationed in Hawaii last August.
Jackson was caught off guard by the proposal, so "it wasn't a fast yes," she tells PEOPLE.
She followed a path of white rose petals and gardenias out to their hotel balcony, where Phillips, 46, arranged a romantic dinner of her favorite foods, including chicken soup. Then, he surprised her with a 17.5-carat diamond ring, hidden under her dessert tray.
"I had no clue," Jackson says. "I couldn't understand why he was so nervous."
When Phillips dropped to his knee, "My heart just stopped," says Jackson, who stars in the reality show Life with La Toya.
"I was in total shock," she says. "We're best friends and we've been business partners forever. It was always professional – no one really crossed those boundaries."
As for wedding plans, Jackson is coy about when she'll head to the altar.
"You have to wait to see the show," she says.
Life with La Toya premieres June 7 on OWN.