I have a walk-in attic. That is, a standard door on the second floor opens up into the space over part of the first floor, and you can enter and walk around. Most of this space contains plywood flooring so you can walk on it. Other, clearly delineated parts, are unfinished, with the bare rafters and insulation open and visible. The unfinished spaces are separated from the walkable parts with 2×4 framing, such that no sane person would want to walk into the unfinished bits without a really good reason.
Lesson for the day: don’t let your mother-in-law wander the attic unattended.