Most bathroom doors in a house are built for privacy, not for rescue. A push-button lock, a thumb-turn, or a sliding latch keeps the door shut while she is inside, and it works fine until the day she needs to get out and cannot, or until someone outside needs to get in and cannot. The change usually comes slowly. The door is still locked, and she is still the one who locks it. What changes is how long the locking and unlocking take, and whether she is still willing to do it alone.
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What to watch for in her own habits
Start with what you can see without asking her anything. Does she stand at the door longer before she opens it? Does she leave it unlatched on purpose, or say she would rather not close it at all? Has she started asking someone to hold the knob, or to stay close while she goes in? Some households notice that the bathroom becomes the one room she avoids until the last possible moment, which is a signal worth taking seriously even if nothing has gone wrong yet.
Then look at the hardware. A latch that sticks in humid weather, a door that has sagged and rubs on the frame, or a lock that has loosened so it turns with more force than before all make it harder to open from the inside. Each one is a small change, and together they add up to a door she no longer trusts.
Check whether someone can open it from outside
Most interior bathroom locks have a small release on the outside of the door, often a narrow slot that takes a flat screwdriver, a coin, or a thin tool. Find it, and keep the tool where a visitor can reach it without searching. Then test the door the way it would be used on a bad day. Close it, lock it, and ask another adult to open it from the hallway. Time how long it takes. If the release is hard to find, if the tool does not fit, or if the door has to be forced, that is the thing to fix first, before any other bathroom change.
When it becomes a question for the care team
Bring it to the care team, the doctor, or whoever coordinates her care when she has been shut in by accident, when she tells you she is afraid to close the door, or when the latch fails after the house has settled or the weather has changed. These are not problems for the family to solve by trying harder at night. They are questions about how she uses the room, what help she needs in it, and whether the plan still fits her. Write down what you saw, when it happened, and what you tried, so the conversation starts from facts.
If you are trying to decide where this sits in the bigger picture, the order to read on this site shows how the house questions connect. You do not need to fix every bathroom issue at once. You need to know who can get through that door, and how fast.