Nan--- thank you for your question and your honesty! Disconnecting from dysfunction is an important thing to know how to do for your own mental health... particularly in a situation like this where you have no "real" investment or knowledge of this person and their integrity. People who feed on drama and negative attention will go to great lengths to find willing "hosts" to feed off of, and this person may truly be in pain--- yet it will be important to ask yourself if you can really trust her, and if the energy you are giving a stranger is really where you'd like to focus your energy?
You speak of using your energy for creativity and happiness--- these are healthy, life-affirming activities, as opposed to sinking into someone else's darkness when it very well could be that they are just sucking your life from you for their own selfish purposes. Boundaries are what you are speaking of--- we all must have defined boundaries in terms of our relationships in this world... meaning, how much will you invest safely, with whom, and when must your own health and defense be taken into consideration? Trying to support and encourage others is a basic human experience and it is good; yet, trying to change someone else or help when the person resists help becomes unhealthy for the helper. This situation has demonstrated that there must be healthy limits in helping--- you can offer encouragement, but to a limit--- once you begin to feel too wrapped up in someone else's drama and pain, it is time to take a step back. She has to 'own' her problems, and choose to be proactive and look for help, rather than being reactive and simply spewing emotion to anyone who will listen. This relieves her pain, yet is simply dumping it on innocent bystanders like you... which in turn makes you partial owner of her burden.
I admire your wish to help--- the world needs more people like you. Just keep your boundaries firm and know that the only person you can truly change is yourself, but that offering support must be done with absolutely no expectations that she will use it for her benefit. You almost have to think of it as a gift you give, and you do it with no expectation that she will use it. Focus on you for a while, and just slowly back away from the computer and the time you spend on Twitter for a bit. Unwrap those tentacles from around you, and take a deep breath... life is happening all around you and you have great things ahead of you! Maybe you will study to go into a helping profession--- and then you will use your powers for good in life! It is ok to not help sometimes, too. People have to earn your trust and respect, and it is ok to surround yourself with people who lift you up as opposed to dragging you down! As a matter of fact, life is much more fun when you do!
Things have a way of working out as they should, and sometimes just observing and not intervening teaches us how that happens. You are not responsible for anyone else's happiness--- you can choose who and when you support and encourage, and never have to be a victim of someone else's circumstances unless you choose to do so.
Hope that helps! Keep up the great work.... and write more music!!