pittsburghgirl - great analysis!
scoops - sounds like you believe MM was hedging her bets - leaving a way to come back if she decided that's what she wanted to do.... very good analysis as well!
The note on top of the boxes - that's what really gets to me. It's a very important clue, but do we know she placed it there herself? Whomever investigated her room might have seen it amongst her things and placed it on top of the boxes, just so it would get lost or as something to look at further...
Photos of her room without anything being disturbed - that what is needed...
ETA: Maybe the placement of the note was something as simple as MM wanting to get rid of it, or taking it with her, and she forgot.... that would be something, with some much be read into it..
It is the same as the "rag in the tailpipe" issue. It could be innocent or a sign. Perhaps, the note was on the floor and she picked it up and placed it on the boxes as she ran out the door. Simple gestures can bring on more meaning when a person disappears. The note could be a sign or it could mean nothing. Yet, the answer may lie somewhere in between. It could mean she was upset with her boyfriend, but it may not also mean she was going to kill herself in NH. There is no doubt she was upset about something though.