Dear K.,
My two-and-a-half-year-old son has a very similar personality type, and we've going through many of the same issues, so yeah, I hear you, sister!
Okay. First of all, I do NOT agree with the posters who say that your daughter is merely being a manipulative drama queen. With all due respect, this is fairly insulting to children (and adults) with sensitive personality types, and to the parents who can clearly see that something is really going on.
However, like all -- well, I'll call them mis-perceptions -- it may have a grain of truth. Do you think there may be a little of both going on? Say, your daughter is genuinely troubled by things that other kids can handle, but when she's genuinely troubled, she looks for ways to get the most comfort possible?
On the discipline front, the wonderful thing about having a sensitive child is that you don't have to do much to get the child's attention: they know right away when you're not happy with them. The really difficult thing is that when you try to correct the behavior, it's so upsetting to the child, you wind up with a whole new set of problems (tantrums, panicking, etc.) on top of the one you were trying to correct.
Here's what I recommend: please let me know if it works. Find a little piece of time (say half an hour) when someone else can watch your son, and have some "girl time" with your daughter. Take her out for ice cream or something. Then tell her frankly that you want to talk to her about the things that make her upset. Start by giving her the list you wrote above, and ask her to add to it. You may be surprised by what you hear. Then tell her, loud and clear, "I understand that those things make you upset, and I want to help. But we need to find something you can do when you're upset that makes you feel better." Then give her some suggestions, "do you want to hug your bear [or any beloved toy]?" "do you want to go to your room and have some quiet time"? "do you want to get out your crayons and color for a minute?" Etc. Be prepared for some completely inappropriate suggestions (eating dessert for breakfast, etc.), but your daughter may actually come up with something that really works. The important thing is to get some buy-in from her.
Then, every time she starts to get worked up (and the earlier you can catch her in a meltdown, the better), redirect her to the activity you've chosen together. She may resist it at times, but here's where it's important to be strict and consistent (though not necessarily mad-sounding). No guarantees of course, but this may help your daughter to develop self-awareness and to begin to learn how to cope with having a sensitive personality type, something that's likely to be part of who she is forever.
Finally, I just want to state clearly (and K., I suspect you know this, this is for a few of the people who posted below), raising a child is not the same as training a puppy. Yes, children need boundaries, and yes, children are capable of being manipulative. But young children are also just beginning to develop self-awareness. The purpose of discipline should not be to generate a certain behavior in an unreflective child; it should be to help children recognize behavior that's not constructive and to begin to redirect themselves.
Best wishes,
Mira
P.S. Sorry, one more thing. In a super-sensitive child, yelling can often backfire (though Lord knows it's tempting at times). It's better to speak *more* quietly when you really want a child to listen. That forces them to quiet down in order to hear you, which in and of itself is calming.