Ugh, notes under the door. I had to endure a toxic tenancy with a nasty piece of work with BPD (Borderline Personality Disorder), which is what it sounds like your "friend" has too. These sort of notes occured on a weekly basis, if not more frequently. I also came back one night to find a large dent in my door where the bastard had punched it, which he never paid to fix, never apologised for and complained about the permanent pain in his hand for for the rest of the year. That was from a trivial falling out over politics, which the asshole did a degree in (and of course, thought validated his opinion as correct and all dissenting opinions as wrong as a result). I ended up sleeping at a friend's most nights for the final month, and actually moved out of the house about a week before the tenancy ended just to get away.

I've tried to empathise with him so many times. I've offered help, I've been soft, I've been firm, but it always followed the cycle of reconciliation, relapse and resent. He's refused any help or acknowledged his own flaws or diagnosis. I simply had to cut him out of my life. It sounds harsh, but on top of the BPD he was really just a manipulative cretin too, especially in his disgusting treatment of women (I continue to hear stories of him abusing positions of power now that I've moved away from Uni and no longer have to suffer his shit first-hand).

I'm sorry, but also kind of relieved, that I'm not the only one who experienced such creepy and unsettling passive-aggressive behaviour on a regular basis.

Edit: If it interests you, here's a list of the symptoms of BPD, which you can compare against her behaviour if you like.