Are you reliant on her for transportation home? And does the door that you would leave by, lock automatically when you leave? In other words, if you leave would you be leaving her dwelling open?
If the door will lock behind you and you are not reliant on her for transportation, leave a note for her and leave quietly - she may be ill.
If you are reliant on her for the transportation, I would suggest that you tap lightly on her door and ask if she feels well enough to take you home.
If the door will not lock behind you automatically, same advice as above - tap on her door and say that you need to leave but don't want to leave her home unlocked.