My sister's game seems to glitch out a lot, basically any item you could interact with would disappear. Not sure why, but restarting the 3DS seems to temporarily fix it. When I go to her town and it happens, things still show up fine on my screen but on hers everything is gone. For example, I'd lie down on a bed, but on her screen I'd just be floating in midair. Also, since all the items are gone, she can stand in the middle of furniture and stuff. Here are a few pictures taken from my point of view: