"Her things are in the kitchen."
Translation:Її речі на кухні.
For some reason kitchen is the only room that uses "на". It's "у ванні" (in the bathroom), "у вітальні" (in the living room), "у спальні" (in the bedroom) and so on, but "на кухні" (in the kitchen).
The only other part of the house that I can think of that uses "на" is "на балконі" (on the balcony), but it's kind of outside of the house so it's not a room to be inside of. Maybe the kitchens used to be treated as an outside part of the household? :)