>>149367799
No.
I actually have a full head-canon as to why Nani goes commando. We see evidence all throughout the film that Nani and Lilo are really struggling, the whole house is a mess and they probably don't have much money. Most women's underwear does not last very long, so I figure that Nani doesn't have that much underwear, and probably doesn't do laundry very often, so she probably only wears underwear when she has to, like when wearing a sarong for work. Most of the time she probably goes commando or is wearing bikini briefs if she's planning on surfing that day.
Hell she probably has more bikinis bottoms than panties because she was a surf champ before her parents died.