"It was really cool, we were all working so my friend had a little, like, girls' night at her house," she tells anchor Matt Lauer, who quickly calls out that the "friend" is none other than Swift. "We had chips and guacamole and pizza."
Gigi also explains how she made her cute cub scout costume.
"I had a really, really intense costume planned and then I said, maybe I'll save it," she shares. "So then I found a cub scout shirt in Japan at a vintage store, and I made a costume out of it."
The beautiful blonde also talks about the interesting look she stepped out in on Tuesday, rocking a gray sweatsuit ensemble with a floor-length white coat. Lauer jokingly told Gigi that he couldn't believe she was willing to drag her coat through the not-so-clean New York City streets.
"This will make you feel better -- the coat came off the runway already dirty," Gigi says with a laugh. "So I walked across the street to get coffee. I only walked across the street. ... It was already dirty, so I either I wear it, or I don't wear it."
Gigi was on the NBC morning show to promote her new Stuart Weitzman boots, which she's proud of since some of the proceeds will go to building schools around the world. Gigi, who's a brand ambassador for the designer shoe label, says having a reputation as someone who's easy to work with is more important than being labeled an "it" girl.
"Obviously, it's an honor to be called that," she notes. "[But] I think that something that I've really paid attention to is just being someone that people like to work with, and I think if you really touch someone on a personal level then they'll be the ones that are fighting for you the next day in a meeting, or pushing you for a certain campaign, and that's something that I just try to stick to."
Last month, Gigi revealed similar advice that her mother, former Real Housewives of Beverly Hills star Yolanda Hadid, imparted on her. Yolanda, 52, is herself a former model.
"I think my favorite thing that she says is, 'When you start working, you better be the most hardworking, nicest person in the room because if you're not, then there's always going to be someone prettier, nicer, and more hardworking,'" Gigi shared with W magazine. "And that's just something that I always think about when I get to set. ... It's always a first impression, and I think that the thing I try and remember is that you have to give your energy for that time, because it's the time that counts, and that's how the person's going to remember you."
While Gigi might describe her Halloween as low-key, of course, not everyone gets to wear the actual Deadpool costume from Ryan Reynolds himself as Swift did at her girls-only bash. Check out more insane Halloween costumes in the video below.