I think she just means it's the first time being on grocery duty for this household. I'm sure she's wandered around a grocery store a bit before. I think for the most part she doesn't have to buy groceries while doing the homestay thing, it makes it easier for them, while providing that immersion factor that living in a dorm wouldn't. And dorms are probably for younger folks anyhow.
Here are Nacky and Chii going shopping together. I'm not sure if it was this one that tipped me off to their living in Rotura. There was a shop sign in the window in the distance that wasn't blurred out.
https://invidious.lunar.icu/watch?v=HUsSzGVkueg
Wow, I've never seen a place that has free snacks for kids before! Not a terrible idea, really. If memory serves, children in Japan behave well in public compared to the West, and you don't get people having loud conversations on the cell phone all over the place. I'm thinking Rotorua must be a tranquil place compared to much of the West.