Strapping on skates, she tells PEOPLE, is a great way to mark the milestone birthday.
"When my daughter Bryn is older I can tell her, 'Look what Mommy did when she was 40,' " says Frankel, who has spent several hours a day for the past two weeks rehearsing with her professional skating partner (his and the other skating pros' identities will soon be revealed by ABC), whom she jokingly refers to as "my ice husband."
In fact, her "ice husband" has already given her a birthday gift.
"He promised he'd give Bryn skating lessons, so when she's 2 she's going to be taught by the best," says Frankel, who will slow down on her birthday to spend it with her real husband, Jason Hoppy, and Bryn, 6 months.
But she won't slow down for long. In between speaking engagements, filming her Bravo reality show and putting the finishing touches on her next book, Frankel has been waking up at 6 a.m. every day to rehearse her first skating routine, which she'll perform on the Skating's Nov. 22 premiere.
"This is one of my childhood fantasies to skate on ice," says Frankel, but "I wouldn't have done this if my husband hadn't said he would help me through it. We talked about – 'Can we do this?' – and he said, 'Yes, I can help you through this.' It is so awesome."
Whether Frankel, who has very little skating experience, will be awesome on ice remains to be seen.
"I used to go to Rockefeller Center as a kid and I used to roller skate but nothing like this," she says. "People ask me, 'Why this show and not Dancing with the Stars?' Dancing is one thing, but to compete on ice skates is such a challenge and when there's something that's a big challenge, I'm all for it."