"It still shocks me!" she tells the magazine. "It's not even normal. I still call him my boyfriend, and he, every once in a while, is like, 'Babe, I'm your fiancé.'"
"He just complements me so well," she continues. "We're very different in a lot of ways. I think really when he became close with my family, and I saw how simpatico everybody was, thats' when I was like, 'Okay, so not only do I love him, but they love him too.' And I feel like that's the way it's supposed to be."
The actress is also an entrepreneur, and will debut her Real Girl's Kitchen lifestyle brand and series on the Cooking Channel in June. While she is excited about the opportunity, she told reporters at the 11th Annual Inspiration Awards that her busy schedule has left her little time for wedding planning.
"I really haven't had any time to sort of Google 'wedding dresses' and Pinterest boards and all the stuff that people I think normally do," she admits. "But in about a week and a half I'm going to get into it."
"We're pretty laid-back, [so] I feel like it'll be easy and casual," she adds. "Not casual, like, you know, linen pants and barefoot, but not super black tie."
Haylie says sister Hilary Duff is always there to support her, and will undoubtedly be involved in her wedding. Hilary married NHL player Mike Comrie in August 2010, but the couple separated in January of this year.
"You know, I think maybe we all think it's a lot weirder than it really is," Haylie says of her sister's estrangement from Comrie. "But we love Mike, and he's still so much a part of our family."
"I think they're doing great," she continues. "They're just taking their time. They're young, you know? So they're not putting stress to figure out which way it's going to go."
Haylie's new program Real Girl's Kitchen premieres June 7 on the Cooking Channel.