I think the problem is not the crazy neighbor at all. You caved in too much when she started complaining. Working with people is fine. Maybe working with them a bit more is OK within reason, especially if they are cordial. But, when you start heeding to all of her demands, it"s only logical to assume she will continue demanding, even if her demands are totally psychotic.
For example, you mentioned that you compromised with her so that you would use your headphones later in the evening. That is edging on unreasonable, but it could go either way. When you agree to use your headphones all the time, that is completely and utterly retarded. She knows she has you by the balls at that point and whats to stop her from making more demands now that she has her foot in the door?
She has no fucking right to call you or your girlfriend, period. She has no right to harass you, your gf or your LL over email or telephone. And, you need to shut that bitch down.
The stories are cool. But, I don"t know how you could live this way. When I moved into my last apartment, we were lucky enough to share a wall with some bass-loving wannabe gangsta. He was unemployed and constantly played some of the most mind-altering bass music that would fill my apartment day and night. We fucking fought that asshole and ending up getting him evicted. If you are being harassed, it"s time to drop the bomb. And, you can even post it here so we can all share in the drama.