Well, I'm not going through this, but I'd like to offer some advice that I could give from my previous experience from my younger brother.
I think that you should sit down and talk to her about the strain she's putting on you. Firstly, your other children deserve attention just as much as she does. Explain to her that she can't do that unless it's a REAL emergency, because if there one day is a real emergency- you may not be as sufficient in believing her because of this. I doubt she'll want to suffer through a real crisis.
If that fails and she doesn't understand, then just ignore her unless it really seems like something's wrong. Remember this always: being a good parent does NOT mean that your child is never upset.
OR here's the funny option. You can do something to teach her a lesson. Tell her that she has the symptoms of a really rare disease. It'll scare her- but hey, she'll learn quick from that. We did this to my younger brother and after that, he shut his mouth unless he was throwing up, he was desprately bleeding or his foot was swollen.
Hope I helped some.