I agree that the best thing to do is see a professional. I have anxiety disorder and depression. At one point they thought it was actually bi polar disorder because I react very similarly, although not to such extremes. I am on some good medication as well that controls. They found I am so sensitive to medication that it takes the lowest dosage to work. Perhaps your daughter will find the same true for her. And it took quite a while to find medication that worked without side effects and then to get the dosage right, so if you decide to go with medication, don't get discouraged if it takes until the sixth or seventh medication to help. You'll usually know within two weeks if it is going to work or not, so it doesn't take that long in reality to find something that helps. It just takes patience and a lot of attention to the mood changes to see if there are bad side effects or good changes.
And since you said the father was bipolar, I am guessing you are pretty skilled in dealing with that in a behavioral way. Anyone who can make it through what you did and come out sane and able to love a daughter showing these symptoms and realize she needs help, well that is an awesome mother.
This is a phase you are going through, and you will get through it. Things will get better. Things will change.
And then you will be able to have more time spread evenly among your three kids. Remember, it is about quality, not quantity, so even if you only get to spend 30 minutes with each one versus an hour that you would like, if it is quality time, they will get so much out of it. The invisible "they" always say that the sign of a good mom is worry if you are good or not, if you are giving your children enough attention. If that is true, that is just more proof that you are a good mom. :) I don't know you that well, but I'm always here if you need someone to say "you can do it, keep on going, you are doing a good job."