"I would be shocked if they're not married before 2012, for sure," Harrison said of Fedotowsky and fiancé Roberto Martinez, who won her heart and proposed in the sixth season of the series.
Harrison says the young couple, who now share an apartment in San Diego, are "doing great" despite pushing back their plans for a spring wedding.
Fedotowsky, who popped up on Monday's episode of The Bachelor, recently began a stint as a correspondent for the local Fox station in San Diego, and Martinez opened a new office for his insurance business last week. Harrison attributes the lovebirds' success as a couple to the normalcy of their lifestyle – and distance from the limelight.
"What I love is that they're living their lives," Harrison told PEOPLE at a Bachelor Blood Drive in Los Angeles. "I try to tell them, 'Don't let The Bachelor change who you are – just let it enhance what you do.' ... I think those successful couples have been able to do that."
Two of the couple's closest friends, Bachelor Pad alum and current couple Tenley Molzhan and Kiptyn Locke agree.
"It's important to be away for a while and get to know each other so then when you go do those things, it's all real," says Locke. "They're so supportive of one another."
Molzhan, who has grown close to Fedotowsky since they competed for Bachelor star Jake Pavelka's heart, admits she's looking forward to a Bachelorette-themed bachelorette party – though she remains tight-lipped about how soon that might happen.
Says Molzhan, "The last I talked to her, she just wanted to enjoy these first things with him: holidays and birthdays and just being able to bring their families together and really enjoy that."