Trapped at a sleeping friend's place

[Seiryuu]

A few hours ago I came over to my friend's place (where she lives with roommates) to study for a final the following day. About an hour or two in she started feeling tired and went back to her room for a nap. Right now I'm in the living room studying but I feel that as a host she should monitor her guests so that nothing happens; the problem is that if I want to leave I believe it to be my obligation to notify her in person that I am (as I have done before many times).

Any advice on what I should do?

UPDATE: Back at my place now after leaving her a note. Thanks for everything, guys.

[Judah]

If you want to leave, leave her a note.

[CharlieBraun]

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.

[Seiryuu]

Thanks for the quick responses, guys.

Leaving her a note seems to be the way to go, as I don't rely on her for transportation. However, she and her roommates always leave the door unlocked (though it is weighted to close behind people) and I don't really want to disturb her sleep because of aforementioned final tomorrow. 

[NyaChan]

Yes do leave her a note - I pulled the disappearing act on my friends twice.  The first person thought it was funny, the second person got freaked out because he didn't see my note on the table and woke up his fiancé and they were both upset.  As for the door - I wouldn't worry about it if they don't.

[Seiryuu]

Back at my place now after leaving a note.

[magician5]

Where is it written that you can't quietly wake her with your "I'm outa here" announcement? That gives her a chance to let you know if she's not doing well, and gives you a chance to make sure she's set her alarm clock (either for more study time, or at least for exam time).

[CharlieBraun]

Back at my place now after leaving a note.

Good luck on the exam!

[Seiryuu]

Back at my place now after leaving a note.

Good luck on the exam!

Thanks! It seemed to go well.

[bopper]

Don't feel too guilty...she thought the visit was "providing you a place to study" and not "chatting with my friend".  She is the one who took a nap, after all!